专题四 · 1002

Posted 2022-11-29 suamfadmp

代码及解释

#include <algorithm>
#include <cmath>
#include <cstdio>
#include <iostream>

// kruskal 求最小生成树，用到并查集

struct Node 
  int x, y;
  double cost;
 g[5005];

int pre[105];

int find(int n)  return n == pre[n] ? n : find(pre[n]); 

bool cmp(Node a, Node b)  return a.cost < b.cost; 

int main() 
  int n;
  while (scanf("%d", &n) != EOF) 
    int k = 0;
    double sum = 0;
    double x[105], y[105];
    for (int i = 1; i <= n; i++)
      scanf("%lf%lf", &x[i], &y[i]);
    for (int i = 1; i <= n; i++)
      for (int j = i + 1; j <= n; j++) 
        g[k].x = i;
        g[k].y = j;
        g[k++].cost = sqrt(fabs((x[i] - x[j]) * (x[i] - x[j]) +
                                (y[i] - y[j]) * (y[i] - y[j])));
      

    for (int i = 1; i <= n; i++)
      pre[i] = i;

    std::sort(g, g + k, cmp);
    for (int i = 0; i < k; i++) 
      int x = find(g[i].x);
      int y = find(g[i].y);
      double z = g[i].cost;
      if (x != y) 
        sum += z;
        pre[x] = y;
      
    
    printf("%.2f\\n", sum);
  
  return 0;