P1332 血色先锋队

题目链接

https://www.luogu.com.cn/problem/P1332

题目思路

还是bfs题，但初始加入队列的有多个元素，所以我就没写成函数形式

题目代码

#include <iostream>
#include <algorithm>
#include <cstring>
#include <queue>

using namespace std;
typedef pair<int, int> PII;
const int N = 510;
PII p[N];
int dist[N][N];
bool st[N][N];
int n, m, a, b;



int main()
{
    memset(dist, -1, sizeof dist);
    queue<PII> q;
    cin >> n >> m >> a >> b;
    for(int i = 0; i < a; i ++ )
    {
        int x, y;
        cin >> x >> y;
        q.push({x, y});
        dist[x][y] = 0;
        st[x][y] = true;
    }
    
    while(q.size())
    {
        auto t = q.front();
        q.pop();
        int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
        for(int i = 0; i < 4; i ++ )
        {
            int a = t.first + dx[i], b = t.second + dy[i];
            if(a >= 1 && a <= n && b >= 1 && b <= m && !st[a][b])
            {
                dist[a][b] = dist[t.first][t.second] + 1;
                st[a][b] = true;
                q.push({a, b});
            }
        }
    }
    for(int i = 0; i < b; i ++ )
    {
        int l, r;
        cin >> l >> r;
        cout << dist[l][r] << endl;
    }
    return 0;
}