Problem A. Breadth First Search

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:256 Mb
Output file:output.txt  

Statement

You are to write a program that receives an unweighted undirected graph and writes all its vertices in order of increasing distance from given vertex S. Distance between vertices A and B is the length of the shortest path from A to B. If there are several vertices such that their distances to S are equal, they may be printed in arbitrary order.

Input file format

Input file contains three integers N, M and S, where M is the number of edges, S is the starting vertex. Vertices are numbered with integer numbers from 1 to N. Each of next M lines contains a pair of integers — numbers of vertices connected by an edge.

Output file format

Output file must contain sequence of vertex numbers sorted by increasing distance from S. If some vertex is not reachable from S, output a single number  − 1.

Constraints

0 ≤ N, M ≤ 100000

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
3 2 1
1 2
2 3
1 2 3

Problem B. Topological sorting

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:8 Mb
Output file:output.txt  

Statement

You are to write a program that performs a topological sorting of a directed graph. Graph contains N vertices, numbered with integers from 1 to N, and M edges.

In other words, given a partial order on numbers from 1 to N, your program must produce some linear order on these numbers which does not conflict with the given partial order.

Input file format

Input file contains two integers N and M, followed by M pairs of integers. Integers in each pair are different, and represent starting and ending vertex of a graph edge.

These pairs may also be considered comparisons where the first number precedes the second one.

Output file format

Output file must contain a permutation of integers from 1 to N — numbers of vertices sorted in topological order. (That is, representing a linear order.) If ordering is not possible, output file must contain a single number  − 1.

Constraints

0 ≤ N, M ≤ 100000

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
4 3
1 2
1 3
3 4
1 3 2 4

Problem C. Dijkstra

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:16 Mb
Output file:output.txt  

Statement

You are to write a program that receives a weighted directed graph and finds distances from source vertex S to all other vertices. Distance from S to some vertex W is the minimal length of path going from S to W. Length of path is the sum of weights of its edges.

Vertices are numbered with integers from 1 to N.

Input file format

First line of input file contains three integers N M and S, where M is the number of edges. Next M lines contain three integers each — starting vertex number, ending vertex number and weight of some edge respectively. All weights are positive. There is at most one edge connecting two vertices in every direction.

Output file format

Output file must contain N integers — distances from source vertex to all vertices. If some vertices are not reachable from S, corresponding numbers must be −1.

Constraints

1 ≤ N ≤ 1000. All weights are less or equal than 1000.

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
5 3 1
1 2 5
1 3 7
3 4 10
0 5 7 17 -1

Problem D. Fast Dijkstra

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:8 Mb
Output file:output.txt  

Statement

You are to write a program that receives a weighted directed graph and finds all distances from fixed vertex S to all other vertices. Distance from S to some vertex W is the minimal length of path going from S to W. Length of path is the sum of weights of its arcs.

Input file format

Input file contains two integers N, M and S. Vertices are numbered with integer numbers from 1 to N. S is the number of source vertex. M is the number of arcs. Each of next M lines contain three integers — numbers of starting and ending vertices of some arc and its weight respectively. All weights are positive. There is at most one arc connecting two vertices in every direction.

Output file format

Output file must contain N numbers. Each I-th number is the distance from vertex S to vertex I. If some vertices are not reachable from S, corresponding numbers must be −1.

Constraints

1 ≤ N, M ≤ 100000 All weights are less or equal 1000.

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
5 3 1
1 2 5
1 3 7
3 4 10
0 5 7 17 -1

Problem E. Shortest Spanning Tree

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:16 Mb
Output file:output.txt  

Statement

You are to write a program that receives a weighted undirected graph and finds length of its shortest spanning tree.

Input file format

Input file contains two integers N, M. Vertices are numbered with integer numbers from 1 to N. M is the number of edges. Each of next M lines contain three integers describing an edge — numbers of vertices, connected by an edge and its weight respectively. All weights are positive. There is at most one edge connecting two vertices.

Output file format

Output file must contain a signle integer number — length of the SST. If it is impossible to construct spanning tree, output file must contain −1.

Constraints

1 ≤ N ≤ 1000 All weights are less or equal 1000.

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
3 3
1 2 10
2 3 10
3 1 10
20

Problem F. SST for sparse graph

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:8 Mb
Output file:output.txt  

Statement

You are to write a program that receives a weighted undirected graph and finds length of its shortest spanning tree.

Input file format

Input file contains two integers N, M. Vertices are numbered with integer numbers from 1 to N. M is the number of edges. Each of next M lines contain three integers describing an edge — numbers of vertices, connected by an edge and its weight respectively. All weights are positive. There is at most one edge connecting two vertices.

Output file format

Output file must contain a signle integer number — length of the SST. If it is impossible to construct spanning tree, output file must contain −1.

Constraints

1 ≤ N, M ≤ 100000 All weights are less or equal 1000.

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
3 3
1 2 10
2 3 10
3 1 10
20

Problem G. Ford-Bellman

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:8 Mb
Output file:output.txt  

Statement

You are to write a program that finds shortest distances from vertex S to all other vertices in a given directed weighted graph. Graph consists of N vertices, numbered from 1 to N, and M edges.

Input file format

Input file contains two integers N M S, followed my M triplets of integers ui vi wi — starting vertex, ending vertex and weight or the edge. There is at most one edge connecting any two vertices in every direction. There are no cycles of negative weight.

Output file format

Output file must contain a vector of N integers — distances from vertex S to other vertices. The distance from any vertex to itself is considered to be 0. If some vertex is not reachable from S, corresponding cell of the vector must contain empty space.

Constraints

0 ≤ N, M ≤ 1000. All weights are less than 1000 by absolute value.

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
3 3 1
1 2 5
1 3 10
2 3 2
0 5 7

Problem H. Floyd-Warshall

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:8 Mb
Output file:output.txt  

Statement

You are to write a program that finds shortest distances between all pairs of vertices in a directed weighted graph. Graph consists of N vertices, numbered from 1 to N, and M edges.

Input file format

Input file contains two integers N and M, followed my M triplets of integers ui vi wi — starting vertex, ending vertex and weight or the edge. There is at most one edge connecting two vertices in every direction. There are no cycles of negative weight.

Output file format

Output file must contain a matrix of size NxN. Element in the j-th column of i-th row mush be the shortest distance between vertices i and j. The distance from the vertex to itself is considered to be 0. If some vertex is not reachable from some other, there must be empty space in corresponding cell of matrix.

Constraints

0 ≤ N ≤ 100. All weights are less than 1000 by absolute value.

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
3 3
1 2 5
1 3 10
2 3 2
0 5 7
  0 2
    0

Problem I. Strong connectivity

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:8 Mb
Output file:output.txt  

Statement

You are to write a program that receives a directed unweighted graph and finds all vertices of its strong-connected component, containing given vertex S.

Input file format

Input file contains two integers N, M and S. Vertices are numbered with integer numbers from 1 to N. M is the number of arcs. Each of next M lines contain pair of integers — starting and ending vertices of some arc respectively. There is at most one arc connecting two vertices in every direction.

Output file format

Output file must contain integer number T — amount of vertices in strong-connected component. After that, there must be T integer numbers in ascending order — vertices of compontent themselves.

Constraints

0 ≤ N, M ≤ 100000.

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
5 4 1
1 2
2 3
3 1
4 1
3 1 2 3

Problem J. Bucket sort

Author:StdAlg   Time limit:3 sec
Input file:input.txt   Memory limit:16 Mb
Output file:output.txt  

Statement

You are to write a program that receives a sequence of words and sorts it in lexicographical order. Linear order on characters is given by ASCII codes.

Input file format

First line of input file contains integer N — the sequence length. Following N lines contain one word per line. Each word is exactly three letters long.

Output file format

Output file must consist of N lines, each containing one word from sorted sequence.

Constraints

0 ≤ N ≤ 1000000.

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
4
KVN
ACM
FSB
GGG
ACM
FSB
GGG
KVN

Problem K. Heapsort

Author:Andrew Stankevich (original idea, text, solution)   Time limit:2 sec
Input file:heapsort.in   Memory limit:64 Mb
Output file:heapsort.out  

Statement

A well known algorithm called heapsort is a deterministic sorting algorithm taking O(n log n) time and O(1) additional memory. Let us describe ascending sorting of an array of different integer numbers.

The algorithm consists of two phases. In the first phase, called heapification, the array of integers to be sorted is converted to a heap. An array a[1…n] of integers is called a heap if for all 1 ≤ i ≤ n the following heap conditions are satisfied:

- if 2in then a[i] > a[2i];

- if 2i + 1 ≤ n then a[i] > a[2i + 1].

We can interpret an array as a binary tree, considering children of element a[i] to be a[2i] and a[2i + 1]. In this case the parent of a[i] is a[i div 2], where i div 2 = floor(i / 2). In terms of trees the property of being a heap means that for each node its value is greater than the values of its children.

In the second phase the heap is turned into a sorted array. Because of the heap condition the greatest element in the heapified array is a[1]. Let us exchange it with a[n], now the greatest element of the array is at its correct position in the sorted array. This is called extract-max.

Now let us consider the part of the array a[1 ... n-1]. It may be not a heap because the heap condition may fail for i=1. If it is so (that is, either a[2] or a[3], or both are greater than a[1]) let us exchange the greatest child of a[1] with it, restoring the heap condition for i=1. Now it is possible that the heap condition fails for the position that now contains the former value of a[1]. Apply the same procedure to it, exchanging it with its greatest child. Proceeding so we convert the whole array a[1 ... n-1] to a heap. This procedure is called sifting down. After converting the part a[1 ... n-1] to a heap by sifting, we apply extract-max again, putting second greatest element of the array to a[n-1], and so on.

For example, let us see how the heap a=(5, 4, 2, 1, 3) is converted to a sorted array. Let us make the first extract-max. After that the array turns to (3, 4, 2, 1, 5). Heap condition fails for a[1] = 3 because its child a[2] = 4 is greater than it. Let us sift it down, exchanging a[1] and a[2]. Now the array is (4, 3, 2, 1, 5). The heap condition is satisfied for all elements, so sifting is over. Let us make extract-max again. Now the array turns to (1, 3, 2, 4, 5). Again the heap condition fails for a[1]; exchanging it with its greatest child we get the array (3, 1, 2, 4, 5) which is the correct heap. So we make extract-max and get (2, 1, 3, 4, 5). This time the heap condition is satisfied for all elements, so we make extract-max, getting (1, 2, 3, 4, 5). The leading part of the array is a heap, and the last extract-max finally gives (1, 2, 3, 4, 5).

It is known that heapification can be done in O(n) time. Therefore, the most time consuming operation in heapsort algorithm is sifting, which takes O(n * log (n)) time.

In this problem you have to find a heapified array containing different numbers from 1 to n, such that when converting it to a sorted array, the total number of exchanges in all sifting operations is maximal possible. In the example above the number of exchanges is 1+1+0+0+0 = 2, which is not the maximum. (5, 4, 3, 2, 1) gives the maximal number of 4 exchanges for n=5.

Input file format

Input file contains n.

Output file format

Output the array containing n different integer numbers from 1 to n, such that it is a heap, and when converting it to a sorted array, the total number of exchanges in sifting operations is maximal possible. Separate numbers by spaces.

Constraints

1 ≤ n ≤ 50000

Sample tests

No. Input file (heapsort.in) Output file (heapsort.out)
1
6
6 5 3 2 4 1

Problem L. Lin-log sort

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:8 Mb
Output file:output.txt  

Statement

You are to write a program that receives a sequence of integer numbers and sorts it, i. e. writes out all elements in ascending order.

Input file format

Input file contains integer N — length of the sequnece, followed by N integer numbers — elements of the sequence.

Output file format

Output file must contain N integer numbers, which must be elements of the source sequence printed in ascending order.

Constraints

0 ≤ N ≤ 100000. Sequence elements are less than 109 by absolute value.

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
5 4 3 10 3 1
1 3 3 4 10

Problem M. Eulerian cycle

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:64 Mb
Output file:output.txt  

Statement

You are to write a program that receives an undirected connected graph and finds its Eulerian cycle.

Input file format

Input file contains two integers N, M. Vertices are numbered with integer numbers from 1 to N. M is the number of edges. Each of following M lines contains a pair of vertex numbers, connected by some edge. There is at most one edge connecting two vertices.

Output file format

Output file must contain a sequence of vertex numbers in order of traversal in an Eiler cycle. If there does not exist any Eiler cycle, output file must contain  − 1.

Constraints

1 ≤ N, M ≤ 100000

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
3 3
1 2
2 3
3 1
1 2 3 1

Задача N. Код Грея

Автор:StdAlg   Ограничение времени:1 сек
Входной файл:input.txt   Ограничение памяти:64 Мб
Выходной файл:output.txt  

Условие

Дана строка, состоящая из N символов 0 и 1. Требуется построить последовательность из всех возможных строк длиной N, состоящих из 0 и 1, такую что:

Формат входного файла

Во входном файле содержится строка из символов 0 и 1

Формат выходного файла

Выходной файл должен содержать 2N строк — искомую последовательность.

Ограничения

1 ≤ N ≤ 15

Примеры тестов

Входной файл (input.txt) Выходной файл (output.txt)
1
1
1
0
2
110
110
111
101
100
000
001
011
010

Problem O. Knuth-Morris-Pratt

Author:StdAlg   Time limit:1 sec
Input file:input.txt   Memory limit:256 Mb
Output file:output.txt  

Statement

You are to write a program that receives two strings and finds position where the second string appears in the first one as a substring.

Input file format

First and second lines of input file contain given strings. Each string is a sequence of lower-case Latin letters from 'a' to 'z' and spaces.

Output file format

Output file must contain a single integer — position of the first occurrence of the substring in a string, or  − 1 if there is none. Positions are numbered from 1.

Constraints

Length of each string does not exceed 100000 characters.

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
yezhiki nachinayut i vyygryvayut
yut
16

Задача P. Ближайшее число

Автор:Известная   Ограничение времени:2 сек
Входной файл:input.txt   Ограничение памяти:256 Мб
Выходной файл:output.txt  

Условие

Дана последовательность из N целых чисел. Для каждого числа вывести ближайшее к нему справа в этой последовательности, которое будет больше него. Для чисел, которым найти ближайшее большее не удалось, вывести сами эти числа.

Формат входного файла

Входной файл содержит целое число N за которым следует N целых чисел ai - исходная последовательность.

Формат выходного файла

В выходной файл необходимо вывести N целых чисел bi, таких что bi является ответом на задачу для числа ai.

Ограничения

1 ≤ N ≤ 106

|ai| ≤ 109

Примеры тестов

Входной файл (input.txt) Выходной файл (output.txt)
1
4 1 2 3 4
2 3 4 4
2
1
1
1

Задача Q. Knapsack problem

Входной файл:input.txt   Ограничение времени:2 сек
Выходной файл:output.txt   Ограничение памяти:64 Мб

Условие

Дана последовательность из N целых чисел. Найдите любую из ее подпоследовательностей, сумма элементов которой равна w, либо установите, что искомой подпоследовательности не существует.

Формат входного файла

Во входном файле находятся числа N и w, а за ними следует последовательность из N целых чисел ai.

Формат выходного файла

Если искомая подпоследовательность существует, выведите N чисел 0 или 1, разделенных пробелами. Единица на позиции i означает, что элемент последовательности ai принадлежит найденной подпоследовательности, 0 означает обратное. В противном случае выведите  − 1.

Ограничения

1 ≤ N ≤ 40, 0 ≤ ai,w ≤ 10000000

Примеры тестов

Входной файл (input.txt) Выходной файл (output.txt)
1
3 7
1 5 6
1 0 1

Problem R. Longest Ordered Subsequence

Author:Far-Eastern Subregional   Time limit:1 sec
Input file:input.txt   Memory limit:8 Mb
Output file:output.txt  

Statement

A numeric sequence of ai is ordered if a1 < a2 < ... < aN. Let the subsequence of the given numeric sequence (a1, a2, ., aN) be any sequence (ai1, ai2, ., aiK), where 1 ≤ i1 < i2 < ... < iK ≤ N. For example, the sequence (1, 7, 3, 5, 9, 4, 8) has ordered subsequences, e. g., (1, 7), (3, 4, 8) and many others. All longest ordered subsequences of this sequence are of length 4, e. g., (1, 3, 5, 8).

Your program, when given the numeric sequence, must find the length of its longest ordered subsequence.

Input file format

The first line of input file contains the length of sequence N. The second line contains the elements of sequence - N integers in the range from 0 to 10000 each, separated by spaces.

Output file format

Output file must contain a single integer - the length of the longest ordered subsequence of the given sequence.

Constraints

1 ≤ N ≤ 1000

Sample tests

No. Input file (input.txt) Output file (output.txt)
1
7
1 7 3 5 9 4 8
4

Задача S. Наибольшая общая подпоследовательность

Автор:-   Ограничение времени:1 сек
Входной файл:input.txt   Ограничение памяти:256 Мб
Выходной файл:output.txt  

Условие

Найдите наибольшую общую подпоследовательность двух строк.

Формат входного файла

В первой строке находится первая строка, во второй строке находится вторая строка. Строки состоят только из маленьких латинских букв.

Формат выходного файла

Вывести наибольшую общую подпоследовательность. Если решений несколько, вывести любое.

Ограничения

Длина каждой строки не менее 1 и не превосходят 1000.

Примеры тестов

Входной файл (input.txt) Выходной файл (output.txt)
1
ababaca
acaba
aaba


0.942s 0.012s 49