B13 多源BFS 矩阵距离

#include <bits/stdc++.h>
using namespace std;

const int N = 1010;
int n, m;
char g[N][N];
struct Node
{
    int x, y;
};
int dis[N][N];
int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, 1, 0, -1};

void bfs()
{
    memset(dis, -1, sizeof dis);
    queue<Node> q;
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
            if (g[i][j] == '1')
                dis[i][j] = 0, q.push({i, j});
    while (q.size())
    {
        auto t = q.front();
        q.pop();
        for (int i = 0; i < 4; i++)
        {
            int a = t.x + dx[i], b = t.y + dy[i];
            if (a < 0 || a >= n || b < 0 || b >= m)
                continue;
            if (dis[a][ b] != -1)
                continue;
            dis[a][ b] = dis[t.x][t.y] + 1;
            q.push({a, b});
        }
    }
}
int main()
{
    cin >> n >> m;
    for (int i = 0; i < n; i++)
        scanf("%s", g[i]);
    bfs();
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
            printf("%d ", dis[i][j]);
        puts("");
    }
    return 0;
}

B13 多源BFS 矩阵距离

#include <bits/stdc++.h>
using namespace std;

const int N = 1010;
int n, m;
char g[N][N];
struct Node
{
    int x, y;
};
int dis[N][N];
int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, 1, 0, -1};

void bfs()
{
    memset(dis, -1, sizeof dis);
    queue<Node> q;
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
            if (g[i][j] == '1')
                dis[i][j] = 0, q.push({i, j});
    while (q.size())
    {
        auto t = q.front();
        q.pop();
        for (int i = 0; i < 4; i++)
        {
            int a = t.x + dx[i], b = t.y + dy[i];
            if (a < 0 || a >= n || b < 0 || b >= m)
                continue;
            if (dis[a][ b] != -1)
                continue;
            dis[a][ b] = dis[t.x][t.y] + 1;
            q.push({a, b});
        }
    }
}
int main()
{
    cin >> n >> m;
    for (int i = 0; i < n; i++)
        scanf("%s", g[i]);
    bfs();
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
            printf("%d ", dis[i][j]);
        puts("");
    }
    return 0;
}