POJ2387 Til the Cows Come Home

前向星+堆优化dijkstra

#include<cstdio>
#include<queue>
#include<cstring>
#include<utility>
using namespace std;
const int maxn = 4e3 + 5;
int ver[maxn], edge[maxn], next[maxn], head[maxn], dis[maxn];
bool vis[maxn];
int tot, n, m;
priority_queue<pair<int,int> > q;
void Add(int x,int y,int z)
{
    ver[++tot] = y, edge[tot] = z, next[tot] = head[x], head[x] = tot;
}
void dijkstra()
{
    memset(dis,0x3f,sizeof(dis));
    memset(vis,0,sizeof(vis));
    q.push(make_pair(0,m));
    dis[m] = 0;
    while(q.size()){
        int x = q.top().second; q.pop();
        if(vis[x]) continue;
        vis[x] = 1;
        for(int i = head[x]; i; i = next[i]){
            int y = ver[i], z = edge[i];
            if(dis[y] > dis[x] + z){
                dis[y] = dis[x] + z;
                q.push(make_pair(-dis[y],y));
            }
        }
    }
}
int main()
{
    int x, y, z;
    scanf("%d%d",&n,&m);
    for(int i = 1; i <= n; i++){
        scanf("%d%d%d",&x,&y,&z);
        Add(x,y,z);
        Add(y,x,z);
    }
    dijkstra();
    printf("%d\n",dis[1]);
    return 0;
}