c++ where memory leak happens in my code?

Question

I was solving simple BFS algorithm

when I submit my code I see memory exclude message .

so I reviewed my code but I could not find memory leak point.

I call vector of vector by reference.

#include <iostream>
#include <vector>
#include <queue>

typedef std::vector<std::vector<int>> vii;

bool canMove(std::pair<int, int> &node, std::pair<int, int> &rule, vii &checker, vii &map, int &R, int &C)
{
    int nextR = node.first + rule.first;
    int nextC = node.second + rule.second;

    // wall check
    if (nextR < 0 || nextR >= R || nextC < 0 || nextC >= C)
        return false;
    if (map[nextR][nextC] == 0)
        return false;

    // not visited || already visited but this is more short way => visit
    if (checker[nextR][nextC] > checker[node.first][node.second] + 1 || checker[nextR][nextC] == 0)
        return true;

    return true;
}

int bfs(vii &map, std::vector<std::pair<int, int>> &rules, vii &checker, int &R, int &C, std::pair<int, int> start)
{
    std::queue<std::pair<int, int>> q;

    // land
    checker[start.first][start.second] = 1;
    q.push(start);

    while (!q.empty())
    {
        std::pair<int, int> node = q.front();
        q.pop();

        for (auto &rule : rules)
        {
            if (canMove(node, rule, checker, map, R, C))
            {
                int nextR = node.first + rule.first;
                int nextC = node.second + rule.second;

                // land
                checker[nextR][nextC] = checker[node.first][node.second] + 1;

                // check result
                if (nextR == R - 1)
                    return checker[nextR][nextC] - 1;

                q.push({nextR, nextC});
            }
        }
    }

    return -1;
}

int main()
{
    int R, C, N;
    std::cin >> R >> C;

    // get map
    std::vector<std::vector<int>> map;
    for (int i = 0; i < R; i++)
    {
        std::vector<int> temp(C, 0);
        for (int j = 0; j < C; j++)
        {
            std::cin >> temp[j];
        }

        map.push_back(temp);
    }

    // get rule
    std::cin >> N;
    std::vector<std::pair<int, int>> rules(N, {0, 0});
    for (int i = 0; i < N; i++)
    {
        std::cin >> rules[i].first;
        std::cin >> rules[i].second;
    }

    // make checker
    std::vector<std::vector<int>> checker;
    for (int i = 0; i < R; i++)
    {
        std::vector<int> temp(C, 0);
        checker.push_back(temp);
    }

    // BFS search
    int result = -1;
    for (int i = 0; i < C; i++)
    {
        if (map[0][i] == 1)
        {
            int bfsResult = bfs(map, rules, checker, R, C, {0, i});
            if (bfsResult)
            {
                result = result == -1 ? bfsResult : std::min(result, bfsResult);
            }
        }
    }

    std::cout << result;

    return 0;
}

here 's my code R and C less than 1000 R, C(1 ≤ R, C ≤ 1,000) memory limit is 256MB

there's few vector of vector of integer but it cannot be higher than 4MB I think because higher R*C is 10^6.

where memory leak happens ?

==== > in detail

input example

4 5
1 0 1 0 1
0 1 1 0 0
1 1 0 1 0
1 0 1 1 1
8
-2 -1
-2 1
-1 -2
-1 2
1 -2
1 2
2 -1
2 1

test site and problem

https://www.acmicpc.net/problem/13903

unfortunately it's using korean. sorry

Answer 1

It seem like the "canMove" function needs to be corrected (or maybe a you have missed a condition). Focus in the last two return statements, you are returning true for both the conditions. Because of which it's causing infinite looping IG.

Answer 2

When you push an element to vector,deck etc., the capacity increases, maybe it will be doubled.

This could be the reason about the memory problem.

To control that, you can use shrink_to_fit function to make the capacity equal to size of the container.

Answer 3

I`m not sure if my answer is helpful, but i think you need to look up the capacity of the vector and deck. The std lib queue is implemented as a deck.