八皇后問題 dfs

要點：將 對角線、列用數組進行標記，加快搜索速度

#include<iostream>
#include<stdio.h>
using namespace std;
int Max = 0;
int m[9][9];
bool A[20] = {false};//右上左下 
bool B[20] = {false};//左上右下
bool C[20] = {false};//列 
void dfs(int deep,int S){
	if(deep==8){
		if(S>Max){
			Max = S;
		}
		return;
	}
	for(int i=1;i<=8;i++){
		if(A[i+deep]==false&&B[i+8-deep-1]==false&&C[i]==false){
			A[i+deep] = true;
			B[i+8-deep-1] = true;
			C[i] = true;
			dfs(deep+1,S+m[deep+1][i]);
			A[i+deep] = false;
			B[i+8-deep-1] = false;
			C[i] = false;
		} 
	}
} 
int main(){
	//freopen("in.txt","r",stdin);
	for(int i=1;i<=8;i++){
		for(int j=1;j<=8;j++){
			cin>>m[i][j];
		}
	}
	dfs(0,0);
	cout<<Max<<'\n';
	return 0;
}