多源最短路Floyd算法

#include<bits/stdc++.h>
#define ll long long 
#define scan(i) scanf("%d",&i)
#define scand(i) scanf("%lf",&i)
#define scanl(i) scanf("%lld",&i)
#define f(i,a,b) for(int i=a;i<=b;i++) 
#define pb(i) push_back(i)
#define ppb pop_back()
#define pf printf
#define dbg(args...) cout<<#args<<" : "<<args<<endl;
using namespace std;
int t,n,m; 
int dis[302][302];
int x,y,w;
void floyd(){
    f(k,0,n-1){
        f(i,0,n-1){
            f(j,0,n-1){
                if(i==j) dis[i][j]=0;
                else dis[i][j]=min(dis[i][j],dis[i][k]+dis[k][j]);
            }
        }
    }
}
int main(){
    scan(t);
    f(kk,1,t){
        scanf("%d%d",&n,&m);
        memset(dis,0x3f,sizeof(dis));
        f(i,1,m){
            scanf("%d%d%d",&x,&y,&w);
            dis[x][y]=w;
        }
        floyd();
        f(i,1,6){
            scanf("%d%d",&x,&y);
            pf("%d
",-dis[y][x]);
            dis[x][y]=-dis[y][x];
            if(i-6) floyd();
        }
        //pf("Case #%d: %lld,kk,ans);
    }
    return 0;
} 

算法复杂度O(n^2)。