2024-09-19 02:22:41 +00:00
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#include <bits/stdc++.h>
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using namespace std;
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int dis[2501];
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2024-09-19 03:11:59 +00:00
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bool exist[2501];//标记每个点是否在queue中
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2024-09-19 02:22:41 +00:00
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struct point
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{
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int to;
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int w;
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};
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int n,m,s,t;
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vector<point> graph[2501];
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void SPFA()
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{
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memset(dis, 0x3f, sizeof(dis));
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2024-09-19 03:11:59 +00:00
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dis[s] = 0; // 注意起 始点是s！！！
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2024-09-19 02:22:41 +00:00
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queue<int> q;
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q.push(s);
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exist[s]=1;
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while(q.size()>0)
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{
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int from=q.front();
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q.pop();
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exist[from]=0;
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for(int i=0;i<graph[from].size();i++)
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{
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// for(int temp:graph[from])
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int to=graph[from][i].to;
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int w=graph[from][i].w;
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if(dis[from]+w<dis[to])
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{
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dis[to]=dis[from]+w;
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if(exist[to]==0)
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{
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q.push(to);
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exist[to]=1;
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}
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}
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}
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}
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}
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int main() {
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ios::sync_with_stdio(false);
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cin.tie(0);
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cin >> n >> m >> s >> t;
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for (int i = 1; i <=m ; i++) {
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int a,b,c;
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cin >> a >> b >> c;
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graph[a].push_back({b,c});
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graph[b].push_back({a,c});
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}
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SPFA();
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cout << dis[t] << endl;
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return 0;
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}
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