Two Paths

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题目链接

Code

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#include <bits/stdc++.h>
#define ka1 getchar()
#define iis std::ios::sync_with_stdio(false)
using namespace std;
typedef long long LL;
const int N = 100005;
const int INF = 0x3f3f3f3f;
const LL mod = 10000;
const double eps = 1e-8;
struct lp{
    int to;
    LL w;
    lp(int a,LL b){to=a;w=b;}
    bool operator <(const lp &a)const {
        if(w!=a.w) return w>a.w;
        return to<a.to;
    }
};
vector<lp>mp[N];
LL dis1[N],dis2[N];
int n,m;
void init(){
    for(int i=0;i<=n;++i)mp[i].clear();
}
void dij(int s){
    memset(dis1,0x3f,sizeof(dis1));
    memset(dis2,0x3f,sizeof(dis2));
    dis1[s]=0;
    priority_queue<lp>Q;
    Q.push(lp(s,0));
    while(!Q.empty() ){
        lp x=Q.top();Q.pop();
        int u=x.to;
        if(dis2[u]<x.w)continue;
        for(int i=0;i<mp[u].size();++i){
            lp y=mp[u][i];
            if(dis2[y.to]>(x.w+y.w)){
                dis2[y.to]=x.w+y.w;
                Q.push(lp(y.to,dis2[y.to]));
            }
            if(dis2[y.to]<dis1[y.to]){
                swap(dis2[y.to],dis1[y.to]);
            }
        }

    }
    printf("%lld\n",dis2[n]);
}
int main(){
    int t;
    scanf("%d",&t);
    while(t--){
        int a,b,c;
        scanf("%d%d",&n,&m);
        init();
        for(int i=0;i<m;++i){
            scanf("%d%d%d",&a,&b,&c);
            mp[a].push_back(lp(b,c));
            mp[b].push_back(lp(a,c));
        }
        dij(1);
    }
    return 0;
}
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