Floyd算法

#include <bits/stdc++.h>

using namespace std;

typedef long long LL;
const int INF = 0x3f3f3f3f;
const int maxn = 10005;
int maps[maxn][maxn];//存图
int dist[maxn][maxn];//存距离
int pre[maxn][maxn];//存i到j路径i的后一个结点
void Floyd(int n) {
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= n; j++) {
            dist[i][j] = maps[i][j];//复制距离
            pre[i][j] = j;//标记i的后一个结点
        }
        for(int k = 1; k <= n; k++)//用k个点对每对顶点进行更新
            for(int i = 1; i <= n; i++)
                for(int j = 1; j <= n; j++) {
                    if(dist[i][k] != INF && dist[k][j] != INF && dist[i][j] > dist[i][k] + dist[k][j]) {
                        dist[i][j] = dist[i][k] + dist[k][j];
                        pre[i][j] = pre[i][k];
                    }
                }
}
void pfpath(int u, int v) { // 打印路径
    while(u != v) {
        cout << u <<" ";
        u = pre[u][v];
    }
    cout << u <<endl;
}
int main() {
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    int n, m, u, v, w;
    while(cin >> n >> m) {
        for(int i = 1; i <= n; i++)
            for(int j = 1; j <= n; j++)
                maps[i][j] = (i == j ? 0 : INF);
        for(int i = 1; i <= m; i++) {
            cin >> u >> v >> w;
            maps[v][u] = maps[u][v] = w;
        }
        Floyd(n);
        cout << dist[1][4] << endl; 
        pfpath(1,4);
    }
    return 0;
}