MST Kruskal普遍实现

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>using namespace std;#define MAXN 10000#define MAXM 1000000#define INF 1<<30//int first[MAXN];struct edge { int u, v, w; }a[MAXM];bool operator<(const edge& a, const edge& b) { return a.w<b.w; }int n, m;int pa[MAXN];//pa[u]  是u的直接父亲，而不是 树根 !!!void init_set() { for(int i=0; i<n; i++) pa[i]=i; }int find_pa(int x){if(pa[x] != x)return pa[x] = find_pa(pa[x]);// pa[x] = find_pa(pa[x])  压缩路径else return x;}void Merge(int u, int v){ pa[find_pa(u)] = find_pa(v); }int isMerge(int u, int v) { return find_pa(u) == find_pa(v); }int exist;int kruskal(){init_set();//!!!!int sum=0, cnt=0;sort(a, a+m);for(int i=0; i<m; i++){int u = a[i].u, v = a[i].v;if(!isMerge(u, v)){sum+=a[i].w;cnt++;Merge(u, v);if(cnt == n-1) {exist=1; break; }}}return sum;}int read_graph(){if(cin>>n>>m){for(int i=0; i<m; i++)cin>>a[i].u>>a[i].v>>a[i].w;return 1;}return 0;}int main(){while(read_graph()){exist = 0;int ans = kruskal();cout<<(exist? ans: -1)<<endl;}}