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# include <bits/stdc++.h>
using namespace std ;
//超详细讲解: https://www.cnblogs.com/cnnnnnn/p/8506883.html
//8皇后问题
# define line 8
void queen ( int i , int j ) ;
int check ( int i , int j ) ;
//棋盘
int chess [ line ] [ line ] ;
//方法总数
int cas = 0 ;
int main ( ) {
//开始尝试
queen ( 0 , 0 ) ;
printf ( " %d \n " , cas ) ;
return 0 ;
}
//皇后的递归主函数
void queen ( int i , int j ) {
if ( j > = line ) {
return ;
}
if ( check ( i , j ) = = 1 ) { //如果能放
chess [ i ] [ j ] = 1 ; //放皇后
if ( i = = line - 1 ) { //如果是最后一行，记录情况
cas + + ;
/*下面是输出每种棋盘结果，供测试*/
for ( int xx = 0 ; xx < 8 ; xx + + )
for ( int yy = 0 ; yy < 8 ; yy + + ) {
printf ( " %d " , chess [ xx ] [ yy ] ) ;
if ( yy = = 7 )
printf ( " \n " ) ;
}
printf ( " \n " ) ;
/*上面是输出结果*/
}
else {
queen ( i + 1 , 0 ) ; //不是最后一行就分析下一行
}
}
//重点代码！！！
chess [ i ] [ j ] = 0 ; //如果此位置不能放， （ ） ，
//如果此位置能放，走到这里就意味着上面的代码全部执行了，把皇后拿走（置零），再讨论其他情况，拿旁边位置试探。
queen ( i , j + 1 ) ;
}
//判断是不是在指定位置放皇后
int check ( int i , int j ) {
int k ;
for ( k = 0 ; k < line ; k + + ) {
if ( chess [ i ] [ k ] = = 1 ) return 0 ; //0=不能放
}
for ( k = 0 ; k < line ; k + + ) {
if ( chess [ k ] [ j ] = = 1 ) return 0 ;
}
for ( k = - line ; k < = line ; k + + ) { //两对角线
if ( i + k > = 0 & & i + k < line & & j + k > = 0 & & j + k < line ) //从左上到右下对角线
if ( chess [ i + k ] [ j + k ] = = 1 ) return 0 ;
if ( i - k > = 0 & & i - k < line & & j + k > = 0 & & j + k < line ) //从左下到右上对角线
if ( chess [ i - k ] [ j + k ] = = 1 ) return 0 ;
}
return 1 ;
}
