52. N-Queens II
The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.
Given an integer n, return the number of distinct solutions to the n-queens puzzle.
实现代码:
class Solution {
public:
int totalNQueens(int n) {
int res =0;
int queenPos[100];
NQueen(res,n,0,queenPos); //从第0行开始摆皇后
return res;
}
void NQueen(int &res,int N, int k,int queenPos[]) { //在0~k-1行皇后已经摆好的情况下,摆第k行及其后的皇后
int i;
if( k == N ) { // N 个皇后已经摆好
res++;
return ;
}
for( i = 0;i < N;i ++ ) { //逐尝试第k个皇后的位置
int j;
for( j = 0; j < k; j ++ ) {
//和已经摆好的 k 个皇后的位置比较,看是否冲突
if( queenPos[j] == i ||abs(queenPos[j] - i) == abs(k-j)) {
break; //冲突,则试下一个位置
}
}
if( j == k ) { //当前选的位置 i 不冲突
queenPos[k] = i; //将第k个皇后摆放在位置 i
NQueen(res,N,k+1,queenPos);
}
} //for( i = 0;i < N;i ++ )
}
};