lightoj 1002

最短路的变形，使用spfa做。

#include<set>#include<map>#include<list>#include<stack>#include<queue>#include<cmath>#include<ctime>#include<cstdio>#include<string>#include<vector>#include<cstring>#include<cstdlib>#include<sstream>#include<iostream>#include<algorithm>using namespace std;#define LL long long#define INF 0x7fffffff#define debug cout << "here" << endl#define CLR(X, Y) memset(X, Y, sizeof X)#define FOR(X, Y) for(int i = X;i < Y;i ++)inline int myMin(int x, int y){return x < y ? x : y;}inline int myMax(int x, int y){return x < y ? y : x;}const int MAXN = 505;int mat[MAXN][MAXN], n;void bfs(int t){    queue<int>Q;    int dist[MAXN], vis[MAXN];    CLR(dist, 1), CLR(vis, 0);    Q.push(t), dist[t] = 0, vis[t] = 1;    while(!Q.empty()){        int u = Q.front();        vis[u] = 0;        Q.pop();        for(int i = 0;i < n;i ++){            if(mat[u][i] > 0){                if(dist[i] > max(mat[u][i], dist[u])){                    dist[i] = max(mat[u][i], dist[u]);                    if(!vis[i]){                        Q.push(i);                        vis[i] = 1;                    }                }            }        }    }    for(int i = 0;i < n;i ++){        if(dist[i] > 20000) printf("Impossible\n");        else printf("%d\n", dist[i]);    }}int main(int argc, char* argv[]){    int t,  m, u, v, w;#ifndef ONLINE_JUDGE    freopen("in.cpp", "r", stdin);#endif    scanf("%d", &t);    int tmp = t;    while(t--){        printf("Case %d:\n", tmp-t);        memset(mat, 0, sizeof mat);        scanf("%d%d", &n, &m);        for(int i = 0;i < m;i ++){            scanf("%d%d%d", &u, &v, &w);            if(mat[u][v] == 0) mat[u][v] = mat[v][u] = w;            else  mat[u][v] = mat[v][u] = min(mat[u][v], w);        }        scanf("%d", &m);        bfs(m);    }    return 0;}