hdu_3631_Shortest Path

//最短路问题，这里要理解flody算法的过程//如果已经marked的点，可以当做中间结点，求出经过这个中间结点所有的最短路#include <cstdio>#include <cstring>#include <algorithm>using namespace std;#define MAXN    331#define INF     0x3f3f3f3fint each_dis[MAXN][MAXN], marked[MAXN];int main(int argc, char const *argv[]){#ifndef ONLINE_JUDGE        freopen("test.in", "r", stdin);#endif        int vertex, arc, ask, u, v, w, cas(1);        while( scanf("%d %d %d", &vertex, &arc, &ask) ) {                if( !vertex && !arc && !ask ) {                        break;                }                if( 1 != cas ) {                        printf("\n");                }                printf("Case %d:\n", cas ++);                for(int i = 0; i < vertex; i ++) {                        for(int j = 0; j < vertex; j ++) {                                each_dis[i][j] = INF;                        }                        each_dis[i][i] = 0;                }                for(int i = 0; i < arc; i ++) {                        scanf("%d %d %d", &u, &v, &w);                        each_dis[u][v] = min(each_dis[u][v], w);                }                memset(marked, 0, sizeof(marked));                for(int t = 0; t < ask; t ++) {                        scanf("%d", &w);                        if( !w ) {                                scanf("%d", &u);                                if( marked[u] ) {                                        printf("ERROR! At point %d\n", u); continue;                                }                                marked[u] = 1;                                for(int i = 0; i < vertex; i ++) {                                        if( INF == each_dis[i][u] ) {                                                continue;                                        }                                        for(int j = 0; j < vertex; j ++) {                                                if( INF == each_dis[u][j] ) {                                                        continue;                                                }                                                each_dis[i][j] = min(each_dis[i][j], each_dis[i][u]+each_dis[u][j]);                                        }                                }                        }                        else {                                scanf("%d %d", &u, &v);                                if( !marked[u] || !marked[v] ) {                                        printf("ERROR! At path %d to %d\n", u, v); continue;                                }                                if( INF == each_dis[u][v] ) {                                        printf("No such path\n"); continue;                                }                                printf("%d\n", each_dis[u][v]);                        }                }        }        return 0;}