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Poj 1151 Invitation Cards dijkstra 堆优化

2024-07-12 08:43:39   222人阅读

很裸的最短路，不过节点数和边数都是1e6，直接dij肯定是不行了，稀疏图用heap优化一下就好

o(╯□╰)o注意STL里面的优先队列是优先级大的（值大的）在前面的，一开始没注意WA了好几发，哎，太粗心了

#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>#include <climits>#include <string>#include <iostream>#include <map>#include <cstdlib>#include <list>#include <set>#include <queue>#include <stack>using namespace std;typedef long long LL;const int maxn = 1000000 + 5;const LL INF = 10000000005LL;int u[maxn],v[maxn],w[maxn];long long d[maxn];int first[maxn],nxt[maxn];bool vis[maxn];int n,m;void add(int _u,int id) {    nxt[id] = first[_u];    first[_u] = id;}struct Node {    long long a;    int b;    Node(long long a,int b):a(a),b(b) {}    bool operator < (const Node &x) const {        return a > x.a;    }};//优先队列优化的dijkstravoid dijkstra(int *v) {    memset(vis,0,sizeof(vis));    for(int i = 1;i <= n;i++) d[i] = INF;    d[1] = 0;    priority_queue<Node> q;    q.push(Node(d[1],1));    while(!q.empty()) {        Node now = q.top(); q.pop();        int x = now.b;        if(vis[x]) continue;        vis[x] = true;        for(int i = first[x];i != 0;i = nxt[i]) {            if(d[v[i]] > d[x] + w[i]) {                d[v[i]] = d[x] + w[i];                q.push(Node(d[v[i]],v[i]));            }        }    }}int main() {    int T; scanf("%d",&T);    for(int kase = 1;kase <= T;kase++) {        memset(first,0,sizeof(first));        memset(nxt,0,sizeof(nxt));;        long long ans = 0;        scanf("%d%d",&n,&m);        for(int i = 1;i <= m;i++) {            scanf("%d%d%d",&u[i],&v[i],&w[i]);            add(u[i],i);        }        dijkstra(v);        for(int i = 1;i <= n;i++) ans += d[i];        memset(first,0,sizeof(first));        memset(nxt,0,sizeof(nxt));        for(int i = 1;i <= m;i++) {            add(v[i],i);        }        dijkstra(u);        for(int i = 1;i <= n;i++) ans += d[i];        cout << ans << endl;    }    return 0;}

　　


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