题面链接

https://www.acwing.com/problem/content/description/852/

思路

和朴素版的Dijkstra类似，只不过我们对边的存储进行堆优化，优先将短的边先更新（基于贪心策略）

代码

#include<bits/stdc++.h>
using namespace std;
//----------------自定义部分----------------
#define ll long long
#define mod 1000000007
#define endl "\n"
#define PII pair<int,int>
#define INF 0x3f3f3f3fint dx[4]={0,-1,0,1},dy[4]={-1,0,1,0};ll ksm(ll a,ll b) {ll ans = 1;for(;b;b>>=1LL) {if(b & 1) ans = ans * a % mod;a = a * a % mod;}return ans;
}ll lowbit(ll x){return -x & x;}const int N = 2e6+10;
//----------------自定义部分----------------
int n,m,q;vector<PII> E[N];
int dis[N];
bool vis[N];void slove(){memset(dis,INF,sizeof dis);dis[1] = 0;priority_queue<PII,vector<PII>,greater<PII> >que;que.push({0,1});while(!que.empty()){PII t = que.top();que.pop();int p = t.second;if(vis[p]) continue;vis[p] = true;for(int i = 0,l = E[p].size(); i < l; ++i){int j = E[p][i].first,k = E[p][i].second;if(dis[j] > dis[p] + k){dis[j] = dis[p] + k;que.push({dis[j],j});}}	}if(dis[n] == INF)cout<<-1<<endl;else cout<<dis[n]<<endl;
}int main()
{std::ios::sync_with_stdio(false);std::cin.tie(nullptr);std::cout.tie(nullptr);cin>>n>>m;int u,v,w;for(int i = 0;i < m; ++i) {cin>>u>>v>>w;E[u].push_back({v,w});}slove();return 0;
}