8皇后问题的解法
傳統辦法-回溯法
#include<iostream>
#include<math.h>
using namespace std;int n=8;
int total=0;
int *c=new int(n);bool is_ok(int row){for(int j=0;j!=row;j++){if(c[row]==c[j] || row-c[row]==j-c[j] || row+c[row]==j+c[j])return false;}return true;
}void queen(int row){if(row==n)total++;elsefor(int col=0;col!=n;col++){c[row]=col;if(is_ok(row))queen(row+1);}
}int main(){queen(0);cout<<total<<endl;return 1;
}
新版方法
#include <iostream>
#include <vector>
#include <algorithm>using namespace std;void N_Queue(vector<int> colum_index, vector<vector<int>>& result, int start);int main()
{int n;cin >> n;vector<int> colum_index;for (int i = 0; i < n; ++i) {colum_index.push_back(i);}vector<vector<int>> res;N_Queue(colum_index, res, 0);cout << res.size() << endl;return 0;
}void N_Queue(vector<int> colum_index, vector<vector<int>>& result, int start)
{if (start == colum_index.size() - 1){bool res = true;for (int i = 0; i < colum_index.size(); i++){for (int j = i + 1; j < colum_index.size(); ++j) {if (i - j == colum_index[i] - colum_index[j] || i - j == colum_index[j] - colum_index[i]){res = false;break;}}if (!res){break;}}if (res){result.push_back(colum_index);}} else{for (int i = start; i < colum_index.size(); i++){swap(colum_index[i], colum_index[start]);N_Queue(colum_index, result, start + 1);swap(colum_index[i], colum_index[start]);}}
}
參考
回溯法
排列法
總結
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