C++代码实现dijkstra算法

以下是C++实现的Dijkstra算法的示例代码：

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

using namespace std;

const int INF = INT_MAX;

typedef pair<int, int> pii;

void dijkstra(vector<vector<pii>>& graph, int start, vector<int>& distance) {
    int n = graph.size();
    priority_queue<pii, vector<pii>, greater<pii>> pq;
    vector<bool> visited(n);

    distance[start] = 0;
    pq.push(make_pair(0, start));

    while (!pq.empty()) {
        int u = pq.top().second;
        pq.pop();

        if (visited[u]) {
            continue;
        }

        visited[u] = true;

        for (auto neighbor : graph[u]) {
            int v = neighbor.first;
            int w = neighbor.second;

            if (distance[u] + w < distance[v]) {
                distance[v] = distance[u] + w;
                pq.push(make_pair(distance[v], v));
            }
        }
    }
}

int main() {
    int n, m;
    cin >> n >> m;

    vector<vector<pii>> graph(n);

    for (int i = 0; i < m; ++i) {
        int u, v, w;
        cin >> u >> v >> w;
        graph[u].push_back(make_pair(v, w));
        graph[v].push_back(make_pair(u, w));
    }

    int start = 0;
    vector<int> distance(n, INF);

    dijkstra(graph, start, distance);

    for (int i = 0; i < n; ++i) {
        cout << "Distance from " << start << " to " << i << " is " << distance[i] << endl;
    }

    return 0;
}

该代码使用了堆优化版的Dijkstra算法，其中 `graph` 是一个邻接表，表示图的结构，`start` 是起点，`distance` 是从起点到各个点的最短距离。