学步园

注意此题可能有重边，所以注意把重边消掉；

code

#include <set>
#include <map>
#include <ctime>
#include <queue>
#include <cmath>
#include <stack>
#include <limits>
#include <vector>
#include <bitset>
#include <string>
#include <cstdio>
#include <cstring>
#include <fstream>
#include <string.h>
#include <iostream>
#include <algorithm>
#define Si set<int>
#define LL long long
#define pb push_back
#define PS printf(" ")
#define Vi vector<int>
#define LN printf("\n")
#define lson l,m,rt << 1
#define rson m+1,r,rt<<1|1
#define SD(a) scanf("%d",&a)
#define PD(a) printf("%d",a)
#define SET(a,b) memset(a,b,sizeof(a))
#define FF(i,a) for(int i(0);i<(a);i++)
#define FD(i,a) for(int i(a);i>=(1);i--)
#define FOR(i,a,b) for(int i(a);i<=(b);i++)
#define FOD(i,a,b) for(int i(a);i>=(b);i--)
#define readf freopen("input.txt","r",stdin)
#define writef freopen("output.txt","w",stdout)
const int maxn = 205;
const int INF = 0xfffffff;
const int dx[]={0,1,0,-1};
const int dy[]={1,0,-1,0};
const double pi = acos(-1.0);
using namespace std;
int dis[maxn],edge[maxn][maxn];
bool vis[maxn];
int main()
{
    int N,M,a,b,x,tmp,k;
    while(~scanf("%d%d",&N,&M)){
        FF(i,N) FF(j,N) edge[i][j]=edge[j][i]=INF;
        SET(vis,false);
        FOR(i,1,M){
            scanf("%d%d%d",&a,&b,&x);
            edge[a][b]=edge[b][a]=min(edge[a][b],x);
        }
        scanf("%d%d",&a,&b);
        FF(i,N) dis[i]=INF;
        FF(i,N){
                dis[i]=edge[a][i];
        }
        //dijstra
        dis[a]=0;
        vis[a]=true;
        FOR(i,1,N-1){
            tmp=INF;
            FF(j,N){
                if(!vis[j] && dis[j]<tmp){
                    tmp=dis[j];
                    k=j;
                }
            }
            if(k==b) break;
            vis[k]=true;
            FF(j,N){
                if(!vis[j] && dis[j] > dis[k]+edge[k][j])
                    dis[j]=dis[k]+edge[k][j];
            }
        }
        if(dis[b]!=INF) printf("%d\n",dis[b]);
        else    puts("-1");

    }
	return 0;
}

floyd代码

#include <set>
#include <map>
#include <ctime>
#include <queue>
#include <cmath>
#include <stack>
#include <limits>
#include <vector>
#include <bitset>
#include <string>
#include <cstdio>
#include <cstring>
#include <fstream>
#include <string.h>
#include <iostream>
#include <algorithm>
#define Si set<int>
#define LL long long
#define pb push_back
#define PS printf(" ")
#define Vi vector<int>
#define LN printf("\n")
#define lson l,m,rt << 1
#define rson m+1,r,rt<<1|1
#define SD(a) scanf("%d",&a)
#define PD(a) printf("%d",a)
#define SET(a,b) memset(a,b,sizeof(a))
#define FF(i,a) for(int i(0);i<(a);i++)
#define FD(i,a) for(int i(a);i>=(1);i--)
#define FOR(i,a,b) for(int i(a);i<=(b);i++)
#define FOD(i,a,b) for(int i(a);i>=(b);i--)
#define readf freopen("input.txt","r",stdin)
#define writef freopen("output.txt","w",stdout)
const int maxn = 1005;
const int INF = 0x3fffffff;
const int dx[]={0,1,0,-1};
const int dy[]={1,0,-1,0};
const double pi = acos(-1.0);
using namespace std;

int N,M,S,T;
int dis[maxn][maxn];

void floyd(){
    FF(k,N) FF(i,N) FF(j,N){
        if(dis[i][k]+dis[k][j] < dis[i][j])
            dis[i][j]=dis[i][k]+dis[k][j];
    }

    if(dis[S][T]!=INF) PD(dis[S][T]);
    else PD(-1);
    LN;
}

int main(){

    while(~scanf("%d%d",&N,&M)){
        FF(i,N) FF(j,N) i==j ? dis[i][j]=0 : dis[i][j]=INF;
        int A,B,X;
        FOR(i,1,M){
            scanf("%d%d%d",&A,&B,&X);
            dis[A][B]=dis[B][A]=min(dis[A][B],X);
        }
        scanf("%d%d",&S,&T);
        floyd();
    }
	return 0;
}