【题目链接】
【算法】
【代码】
#include<bits/stdc++.h> using namespace std; const int INF = 2e9; struct point { int x,y; } a[100]; int i,j,ans,n,Mask,t; int val[9][9]; int w[2000],num[2000]; bool used[100]; int row[10],col[10],grid[10]; bool solved; const int s[9][9] = { {6,6,6,6,6,6,6,6,6}, {6,7,7,7,7,7,7,7,6}, {6,7,8,8,8,8,8,7,6}, {6,7,8,9,9,9,8,7,6}, {6,7,8,9,10,9,8,7,6}, {6,7,8,9,9,9,8,7,6}, {6,7,8,8,8,8,8,7,6}, {6,7,7,7,7,7,7,7,6}, {6,6,6,6,6,6,6,6,6} }; inline int lowbit(int x) { return x & (-x); } inline void chkmax() { int i,ret = 0; for (i = 0; i < 9; i++) { for (j = 0; j < 9; j++) { ret += val[i][j] * s[i][j]; } } ans = max(ans,ret); } inline void dfs(int dep) { int i,mn,pos,v,t; if (dep > n) { solved = true; chkmax(); return; } else { v = 0; mn = INF; for (i = 1; i <= n; i++) { if (!used[i]) { t = row[a[i].x] & col[a[i].y] & grid[a[i].x/3*3+a[i].y/3]; if (!t) continue; if (w[t] < mn) { mn = w[t]; pos = i; v = t; } } } while (v) { used[pos] = true; val[a[pos].x][a[pos].y] = num[lowbit(v)] + 1; row[a[pos].x] ^= lowbit(v); col[a[pos].y] ^= lowbit(v); grid[a[pos].x/3*3+a[pos].y/3] ^= lowbit(v); dfs(dep+1); used[pos] = false; row[a[pos].x] ^= lowbit(v); col[a[pos].y] ^= lowbit(v); grid[a[pos].x/3*3+a[pos].y/3] ^= lowbit(v); val[a[pos].x][a[pos].y] = 0; v -= lowbit(v); } } } int main() { Mask = (1 << 9) - 1; for (i = 0; i <= Mask; i++) { w[i] = 0; t = i; while (t) { w[i]++; t -= lowbit(t); } } for (i = 0; i < 9; i++) num[1 << i] = i; for (i = 0; i < 9; i++) row[i] = col[i] = grid[i] = Mask; for (i = 0; i < 9; i++) { for (j = 0; j < 9; j++) { scanf("%d",&val[i][j]); if (!val[i][j]) { n++; a[n] = (point){i,j}; } else { row[i] ^= (1 << (val[i][j] - 1)); col[j] ^= (1 << (val[i][j] - 1)); grid[i/3*3+j/3] ^= (1 << (val[i][j] - 1)); } } } solved = false; dfs(1); if (solved) printf("%d\n",ans); else printf("-1\n"); return 0; }
原文：https://www.cnblogs.com/evenbao/p/9277767.html