#include <bits/stdc++.h> using namespace std; const int N = 3e5 + 10; int n, m, a[N], d[N][2]; vector <int> g[N], ord; bool was[N]; bool check(int f) { for (int i = 1; i <= n; i++) was[i] = false; int cnt = 0; for (int x : ord) { was[x] = true; d[x][0] = 1e9; d[x][1] = (a[x] == 1 ? 0 : -1e9); for (int y : g[x]) { if (!was[y]) continue; d[x][0] = min(d[x][0], d[y][0] + 1); d[x][1] = max(d[x][1], d[y][1] + 1); } if (d[x][0] + d[x][1] <= f) d[x][1] = -1e9; if (d[x][1] == f) cnt++, d[x][0] = 0, d[x][1] = -1e9; } if (d[1][1] >= 0) cnt++; return cnt <= m; } void dfs(int x, int fa) { for (int y : g[x]) if (y != fa) dfs(y, x); ord.push_back(x); } int main() { scanf("%d%d", &n, &m); for (int i = 1; i <= n; i++) scanf("%d", &a[i]); for (int i = 1; i < n; i++) { int x, y; scanf("%d%d", &x, &y); g[x].push_back(y); g[y].push_back(x); } dfs(1, 1); int l = 0, r = 1e9, ans = 0; while (l <= r) { int mid = l + r >> 1; if (check(mid)) ans = mid, r = mid - 1; else l = mid + 1; } printf("%d\n", ans); }

dyn.cpp: In function 'int main()':
dyn.cpp:41:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   41 |         int mid = l + r >> 1;
      |                   ~~^~~
dyn.cpp:30:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   30 |     scanf("%d%d", &n, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~
dyn.cpp:31:39: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   31 |     for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
      |                                  ~~~~~^~~~~~~~~~~~~
dyn.cpp:34:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   34 |         scanf("%d%d", &x, &y);
      |         ~~~~~^~~~~~~~~~~~~~~~