1129.热浪

算法：

堆优化dijkstra，不过起点是题目给的，所以初始化时dist[ts]=0,之前一直写的dist[1]=0,淦。

代码：

#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>

using namespace std;

typedef pair<int, int> PII;

int n,m,ts,te;
const int N = 2510,M=6200*2+10;
int h[N], e[M], w[M], ne[M], idx;
int dist[N];
bool st[N];

void add(int a, int b, int c)  // 添加一条边a->b，边权为c
{
    e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx ++ ;
}


void dijkstra()  // 求ts号点到te号点的最短路距离
{
    memset(dist, 0x3f, sizeof dist);
    dist[ts] = 0;
    priority_queue<PII, vector<PII>, greater<PII>> heap;
    heap.push({0, ts});

    while (heap.size())
    {
        auto t = heap.top();
        heap.pop();

        int ver = t.second, distance = t.first;

        if (st[ver]) continue;
        st[ver] = true;

        for (int i = h[ver]; i != -1; i = ne[i])
        {
            int j = e[i];
            if (dist[j] > dist[ver] + w[i])
            {
                dist[j] = dist[ver] + w[i];
                heap.push({dist[j], j});
            }
        }
    }
}

int main()
{

    cin>>n>>m>>ts>>te;
    memset(h, -1, sizeof h);
    for(int i=0;i<m;i++){
        int a,b,c;
        cin>>a>>b>>c;
        add(a, b, c);
        add(b, a, c);
    }
    dijkstra();
    cout<<dist[te];
    return 0;
}

时间复杂度：$o(nlogn)$