hihocoder #1109 最小生成树三·堆优化的Prim算法

#include<fstream>
#include<iostream>
#include<string.h>
#include<math.h>
using namespace std;
#define FOR(i,b,e) for(int i=(b);i<=(e);i++)
#define FORE(i,b,e) for(int i=(b);i>=(e);i--)
#define lson(x) (x<<1)
#define rson(x) ((x<<1)+1)
#define maxnum  100003
#define maxedge 1000003
#define INF     100003
struct edge{
int nxt;
int v;
int val;
}e[maxedge*2];
int edgenum=0;
int head[maxnum];
int heap[2*maxedge],heapnum=0;
bool visit[maxnum];

int pop_heap(){
int res=heap[1];
int h=heap[heapnum];
heapnum--;

int hole = 1;
while(hole <= heapnum){
int index=hole<<1;
if(index>heapnum) break;
index = (index+1>heapnum||e[heap[index]].val<=e[heap[index+1]].val)?index:index+1;
if(e[heap[index]].val<e[h].val)
heap[hole]=heap[index];
else break;
hole=index;

}
heap[hole]=h;
return res;
}

void insert(int ed){
int i=++heapnum;
while(i>1&&e[heap[i/2]].val>e[ed].val){
heap[i]=heap[i/2];
i/=2;
}
heap[i]=ed;
}

int main()
{
#ifdef DEBUG_
ifstream fin("G:/1.txt");
#define cin fin
#endif
int N,M,u,v,val;
memset(e,0,sizeof(e));
memset(head,-1,sizeof(head));
memset(visit,0,sizeof(visit));
cin>>N>>M;
FOR(i,0,M-1){
cin>>u>>v>>val;
e[edgenum].v=v;
e[edgenum].val=val;
e[edgenum].nxt=head[u];
head[u]=edgenum++;
e[edgenum].v=u;
e[edgenum].val=val;
e[edgenum].nxt=head[v];
head[v]=edgenum++;
}

int res = 0;
int left = N - 1;
visit[1] = true;
for (int i = head[1]; i != -1; i = e[i].nxt)
insert(i);

while (heapnum!=0 && left) {
int ed = pop_heap();
if (visit[e[ed].v])
continue;
res += e[ed].val;
left--;
visit[e[ed].v] = true;
for (int i = head[e[ed].v]; i != -1; i = e[i].nxt) {
if (!visit[e[i].v])
insert(i);
}
}

cout<<res<<endl;
return 0;
}