11573 - Ocean Currents

這題必須要加優先隊列優化 不然會超時

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <queue>
using namespace std;
const int maxn = 1000 + 7;
const int INF = ~0U >> 1;
const int dx[] = {-1, -1, 0, 1, 1, 1, 0, -1};
const int dy[] = {0, 1, 1, 1, 0, -1, -1, -1};
char str[maxn][maxn];
struct node {
    int x, y;
    int val;
    node(int a, int b, int c) : x(a), y(b), val(c) { }
    bool operator<(const node &rhs) const {
        return val > rhs.val;
    }
};
int m, n;
int q, sx, sy, ex, ey;
int vis[maxn][maxn];

int BFS() {
    int ans = INF;
    priority_queue<node> que;
    memset(vis, -1, sizeof(vis));
    vis[sx][sy] = 0;
    que.push(node(sx, sy, 0));
    while(!que.empty()) {
        node u = que.top(); que.pop();
        if(u.x == ex && u.y == ey) {
            return u.val;
        }
        for(int i = 0; i < 8; ++i) {
            int nx = dx[i] + u.x, ny = dy[i] + u.y;
            if(nx >= 1 && nx <= m && ny >= 1 && ny <= n) {
                int d = u.val;
                if(str[u.x][u.y] - '0' != i) d += 1;
                if(vis[nx][ny] == -1 || vis[nx][ny] > d) {
                    vis[nx][ny] = d;
                    que.push(node(nx, ny, d));
                }
            }
        }
    }
    return ans;
}

int main() {
    while(scanf("%d%d", &m, &n) != EOF) {
        for(int i = 1; i <= m; ++i)
            scanf("%s", str[i] + 1);
        scanf("%d", &q);
        for(int i = 0; i < q; ++i) {
            scanf("%d%d%d%d", &sx, &sy, &ex, &ey);
            int ans = BFS();
            printf("%d\n", ans);
        }

    }
    return 0;
}