不能用kruskal么？

#include <vector>
#include <iostream>
#include <queue>
#include <algorithm>
#include <set>
#include <map>
#include <cmath>
#include <climits>
#include <stack>
#include <cstdio>
#include <map>

using namespace std;

struct edge {
   int src;
   int dest;
   long long dis;
};

bool cmp(const edge& a, const edge& b) {
   return a.dis < b.dis;
}

int father(vector<int>& f, int i) {
   if (f[i] != i) {
      return f[i] = father(f, f[i]);
   } else {
      return i;
   }
}

int main() {
   //freopen("P4955_6.in", "r", stdin);

   int m, n;

   cin >> m >> n;

   vector<edge> e;
   vector<vector<long long>> grid(m, vector<long long>(n));
   vector<vector<int>> waypoint(m, vector<int>(n));

   for (int i = 0; i < m; ++i) {
      for (int j = 0; j < n; ++j) {
         cin >> grid[i][j];
      }
   }

   int count = 0;
   for (int i = 0; i < m; ++i) {
      for (int j = 0; j < n; ++j) {
         cin >> waypoint[i][j];
         count += waypoint[i][j];
      }
   }

   for (int i = 0; i < m; ++i) {
      for (int j = 0; j < n; ++j) {
         if (j + 1 < n) {
            e.push_back({i * n + j, i * n + j + 1, abs(grid[i][j] - grid[i][j + 1])});
         }
         if (i + 1 < m) {
            e.push_back({i * n + j, (i + 1) * n + j, abs(grid[i][j] - grid[i + 1][j])});
         }
      }
   }

   sort(e.begin(), e.end(), cmp);

   vector<int> f(m * n);
   for (int i = 0; i < f.size(); ++i) {
      f[i] = i;
   }

   long long ans = 0;
   for (int i = 0; i < e.size() && count; ++i) {
      int sf = father(f, e[i].src);
      int df = father(f, e[i].dest);
      if (sf != df) {
         f[df] = sf;
      } else {
         continue;
      }

      int si = e[i].src / n;
      int sj = e[i].src % n;

      int di = e[i].dest / n;
      int dj = e[i].dest % n;

      if (waypoint[si][sj]) {
         waypoint[si][sj] = 0;
         count--;
      }
      if (waypoint[di][dj]) {
         waypoint[di][dj] = 0;
         count--;
      }
      ans = e[i].dis;
   }

   cout << ans;

   return 0;
}