用C++写一个bellman-ford算法

好的，下面是C++实现的Bellman-Ford算法代码：

#include <iostream>
#include <vector>
#include <climits>

using namespace std;

struct Edge {
    int from, to, cost;
    Edge(int f, int t, int c) : from(f), to(t), cost(c) {}
};

vector<int> bellmanFord(vector<Edge>& edges, int n, int start) {
    vector<int> dist(n, INT_MAX);
    dist[start] = 0;
    for (int i = 0; i < n - 1; i++) {
        for (int j = 0; j < edges.size(); j++) {
            Edge e = edges[j];
            if (dist[e.from] != INT_MAX && dist[e.to] > dist[e.from] + e.cost) {
                dist[e.to] = dist[e.from] + e.cost;
            }
        }
    }
    return dist;
}

int main() {
    int n = 5;
    vector<Edge> edges;
    edges.push_back(Edge(0, 1, 1));
    edges.push_back(Edge(0, 2, 5));
    edges.push_back(Edge(1, 2, 2));
    edges.push_back(Edge(1, 3, 2));
    edges.push_back(Edge(1, 4, 1));
    edges.push_back(Edge(2, 3, 1));
    edges.push_back(Edge(2, 4, 3));
    edges.push_back(Edge(3, 4, 1));
    vector<int> dist = bellmanFord(edges, n, 0);
    for (int i = 0; i < n; i++) {
        cout << "Distance from vertex 0 to vertex " << i << " is " << dist[i] << endl;
    }
    return 0;
}

该算法的输入是边的集合`edges`，顶点总数`n`和起点`start`。输出为从起点到每个顶点的最短距离。实现中使用了一个数组`dist`来存储每个顶点到起点的距离，初始值为无穷大，起点的值为0。然后通过n-1次循环，遍历所有的边，更新`dist`数组中的值。如果某个顶点的距离被更新了，则表明它可以通过更短的路径到达起点。如果在n-1次循环后还存在可以更新的顶点，则说明图中存在负权环路，此时算法无法求出最短路径。