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
");
        else printf("%d
", 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:
", 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;
}