SPFA算法模板

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#include<iostream>#include<cstdio>#include<queue>#include<cstring>using namespace std;const int size = 200010;int head[size],next[size],dist[size];struct dc{    int t,d;}l[size];bool use[size];int pri[size];int t,c,s,e;int tot = 1;void build(int f,int t,int d){    l[tot].d = d;    l[tot].t = t;    next[tot] = head[f];    head[f] = tot ++;}queue < int > q;void spfa(int s){    dist[s] = 0;    use[s] = 1;    q.push(s);    while(!q.empty())    {        int f = q.front();        q.pop();        use[f] = 0;        for(int i = head[f] ; i ; i = next[i])        {            int t = l[i].t;            if(dist[t] > dist[f] + l[i].d)            {                dist[t] = dist[f] + l[i].d;                pri[t] = f;                if(!use[t])                {                    use[t] = 1;                    q.push(t);                }            }        }    }}int main(){    scanf("%d%d%d%d",&t,&c,&s,&e);    for(int i = 1 ; i <= t ; i ++)        dist[i] = 214748364;    for(int i = 1 ; i <= c ; i ++)    {        int f,t,d;        scanf("%d%d%d",&f,&t,&d);        build(f,t,d);        build(t,f,d);    }    spfa(s);    printf("%d",dist[e]);    return 0;}

例题codevs1557 , 两点间的最短路径

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