最小生成树(无向图)
Kruskal
给所有边按从小到大排序 形成环则不选择(利用并查集)
P1546 最短网络 https://www.luogu.com.cn/problem/P1546
#include<iostream> #include<cstdio> #include<string> #include<algorithm> typedef long long ll; using namespace std; struct Node { int x, y, w; friend bool operator < (const Node& a, const Node& b) { return a.w < b.w; } }; Node a[200002]; int pre[200002]; int Find(int x) { return pre[x] == x ? x : pre[x] = Find(pre[x]); } int main() { int n, k, cnt = 0; scanf("%d", &n); for (int i = 0; i < n; i++) { pre[i] = i; for(int j=0;j<n;j++){ scanf("%d", &k); if (j > i) { //矩阵只需判断一半 a[cnt].x = i; a[cnt].y = j; a[cnt++].w = k; } } } sort(a, a + cnt); int ans = 0; int p = 0; for (int i = 0; i <cnt; i++) { if (Find(a[i].x) != Find(a[i].y)) { ans += a[i].w; pre[Find(a[i].x)] = a[i].y; p++; if (p == n - 1) break; } } printf("%d\n", ans); return 0; }