可以通过并查集查看a,b的根结点是否相同,相同则代表连通,即会成环不能加入最小生成树
#include <iostream> #include <cstdio> #include <cstring> #include <algorithm> using namespace std; const int N = 1e5 + 10, M = 2e5 + 10; struct Edge{ int a, b, c; bool operator<(const Edge &t){ return c < t.c; } }edge[M]; int p[N], n, m; int find(int x) { if(p[x] != x) p[x] = find(p[x]); return p[x]; } int Kruskal() { int pa, pb; int res = 0, cnt = 0; sort(edge, edge+m); for(int i = 0; i < m; ++i) { pa = find(edge[i].a), pb = find(edge[i].b); if(pa != pb) //不连通即不成坏 res += edge[i].c, p[pa] = pb, cnt++; } if(cnt < n-1) return 0x3f3f3f3f; return res; } int main() { scanf("%d%d",&n, &m); for(int i = 1; i <= n; ++i) p[i] = i; int a, b, c; for(int i = 0; i < m; ++i) { scanf("%d%d%d",&a, &b, &c); edge[i] = {a, b, c}; } int res = Kruskal(); if(res == 0x3f3f3f3f) cout << "impossible" << endl; else cout << res << endl; return 0; }