计蒜客 八皇后问题
#include <bits/stdc++.h>
using namespace std;
using namespace std;
#define maxn 8
int board[maxn][maxn];
int maxSum = 0;
//值:第0 1 2 3 4....(数组下标)列的皇后在第几行
int queenAtRows[maxn] = {-1};
//第0 1 2 3 4....行是否有皇后
bool rowStatus[maxn] = {false};
//第0 1 2 3 4....正斜线是否有皇后
bool passiveStatus[2 * maxn] = {false};
//第0 1 2 3 4....反斜线是否有皇后
bool negativeStatus[2 * maxn] = {false};
/*
@idx:现在在放第idx个皇后
*/
void dfs(int idx) {
//递归基
if(idx >= maxn) {
int sum = 0;
for(int col = 0; col < maxn; ++col) { //第col列皇后
for(int row = 0; row < maxn; ++row) {
if(queenAtRows[col] == row)
sum += board[row][col];
}
}
maxSum = max(maxSum, sum);
return;
}
for(int queenAtRow = 0; queenAtRow < maxn; ++queenAtRow) { //一行一行的尝试放置皇后
if(!rowStatus[queenAtRow] && !passiveStatus[idx + queenAtRow] && !negativeStatus[idx - queenAtRow + maxn - 1]) {
rowStatus[queenAtRow] = true;
passiveStatus[idx + queenAtRow] = true;
negativeStatus[idx - queenAtRow + maxn - 1] = true;
queenAtRows[idx] = queenAtRow;
dfs(idx + 1);//递归尝试放下1个皇后
//复原现场,回溯法需要重点注意的地方
rowStatus[queenAtRow] = false;
passiveStatus[idx + queenAtRow] = false;
negativeStatus[idx - queenAtRow + maxn - 1] = false;
}
}
}
int main() {
//freopen("data.in", "r", stdin);
for(int i =0; i < maxn; i++) {
for(int j = 0; j < maxn; j++) {
cin >> board[i][j];
}
}
dfs(0);
cout << maxSum << endl;
return 0;
}