POJ 3669 Meteor Shower

POJ_3669

    广搜一下即可。

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<queue>
#define MAXD 310
#define INF 0x3f3f3f3f
int N, danger[MAXD][MAXD], dis[MAXD][MAXD];
int dx[] = {-1, 1, 0, 0, 0}, dy[] = {0, 0, -1, 1, 0};
int inside(int x, int y)
{
    return x >= 0 && y >= 0;
}
void init()
{
    int i, j, x, y, t, nx, ny;
    memset(danger, 0x3f, sizeof(danger));
    for(i = 0; i < N; i ++)
    {
        scanf("%d%d%d", &x, &y, &t);
        for(j = 0; j < 5; j ++)
        {
            nx = x + dx[j], ny = y + dy[j];
            if(!inside(nx, ny)) continue;
            danger[nx][ny] = std::min(danger[nx][ny], t);
        }
    }
}
struct St
{
    int x, y;
    St(){}
    St(int _x, int _y) : x(_x), y(_y){}
};
void solve()
{
    int i, j, x, y;
    std::queue<St> q;
    if(danger[0][0] == 0)
    {
        printf("-1\n");
        return ;
    }
    memset(dis, 0x3f, sizeof(dis)), dis[0][0] = 0;
    q.push(St(0, 0));
    while(!q.empty())
    {
        St st = q.front();
        if(danger[st.x][st.y] == INF) break;
        q.pop();
        for(i = 0; i < 4; i ++)
        {
            x = st.x + dx[i], y = st.y + dy[i];
            if(inside(x, y) && dis[st.x][st.y] + 1 < dis[x][y] && danger[x][y] > dis[st.x][st.y] + 1)
                dis[x][y] = dis[st.x][st.y] + 1, q.push(St(x, y));
        }
    }
    if(q.empty()) printf("-1\n");
    else
    {
        St st = q.front();
        printf("%d\n", dis[st.x][st.y]);
    }
}
int main()
{
    while(scanf("%d", &N) == 1)
    {
        init();
        solve();
    }
    return 0;
}