MST 比较水。给出的M个直接合并就好。边权就还是DIST；
或者直接M个点对的边权直接设置为0
#include <map> #include <set> #include <list> #include <cmath> #include <ctime> #include <deque> #include <stack> #include <queue> #include <cctype> #include <cstdio> #include <string> #include <vector> #include <climits> #include <cstdlib> #include <cstring> #include <iostream> #include <algorithm> #define LL long long #define PI 3.1415926535897932626 using namespace std; int gcd(int a, int b) {return a % b == 0 ? b : gcd(b, a % b);} #define MAXN 755 int p[MAXN]; int N,M,cas; int Find(int x) {return x == p[x] ? x : p[x] = Find(p[x]);} struct node { int x,y; }src[MAXN]; struct dis { int u,v; double dist; friend bool operator < (const dis &a,const dis &b) { return a.dist < b.dist; } }d[MAXN*MAXN]; void read() { cas = 0; for (int i = 1; i <= N; i++) scanf("%d%d",&src[i].x,&src[i].y); for (int i = 1; i <= N; i++) for (int j = i + 1; j <= N; j++) { d[cas].u = i; d[cas].v = j; d[cas++].dist = sqrt((double)((src[j].x - src[i].x) * (src[j].x - src[i].x)) + (double)((src[j].y - src[i].y) * (src[j].y - src[i].y))); } sort(d,d + cas); scanf("%d",&M); for (int i = 0; i <= N; i++) p[i] = i; while (M--) { int u,v; scanf("%d%d",&u,&v); int x = Find(u) , y = Find(v); if (x != y) p[x] = y; } } double kruskal() { double ans = 0; for (int i = 0; i < cas; i++) { int u = d[i].u , v = d[i].v ; double w = d[i].dist; int x = Find(u) , y = Find(v); if (x != y) { ans += w; p[x] = y; } } return ans; } int main() { while (scanf("%d",&N) != EOF) { read(); printf("%.2lf ",kruskal()); } return 0; }