牛客855512997号：第一题用的二分，0.7

咕咕咕_：拒绝长代码（雾 #include <bits/stdc++.h> using namespace std; int sqr(int x) {return x * x;} void chmin(int &x, int y) {if (x > y) x = y;} int dp[1 << 20], n, m, a[21], vis[1 << 20], S, ans; char s[25]; int main() {   cin >> n >> m;   for (int i = 0; i < n; ++i) {     cin >> s;     for (int j = 0; j < m; ++j) if (s[j] == '1') a[i] |= 1 << j;   }   for (int S = 0; S < (1 << n); ++S)      for (int i = 0; i < n; ++i) if (S & (1 << i)) vis[S] |= a[i];   memset(dp, 0x3f, sizeof dp);   dp[0] = 0;   for (int S = 0; S < (1 << n); ++S) {     for (int i = 0; i < n; ++i)        if (!(S & (1 << i))) chmin(dp[S | (1 << i)], dp[S] +             sqr(__builtin_popcount(vis[S | (1 << i)] ^ (vis[S | (1 << i)] & vis[S]))));   }   cout << dp[(1 << n) - 1];   return 0; }