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Nqueens.cc
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Nqueens.cc
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#include <iostream>
#include <vector>
#include <string>
using namespace std;
class Solution {
public:
vector<vector<string> > ret;
vector<vector<string> > solveNQueens(int n) {
if (n <= 0)
return ret;
int row[n];
for (int i = 0; i < n; i++) row[i] = -1;
doRecur(0, row, n);
return ret;
}
void doRecur(int i, int *row, const int n) {
if (i == n) {
//cout << "n is " << n << endl;
vector<string> tmp(n * n, ".");
for (int j = 0; j < n; j++) {
tmp[n * row[j] + j] = "Q";
}
ret.push_back(tmp);
return;
}
for (int j = 0; j < n; j++) {
bool valid = true;
for (int k = 0; k < i; k++) {
if (row[k] == j || (abs(k - i) == abs(row[k] - j))) {
valid = false;
break;
}
}
if (valid) {
row[i] = j;
doRecur(i + 1, row, n);
row[i] = -1;
}
}
return;
}
};
int main() {
Solution sol;
int n = 4;
vector<vector<string> > ret = sol.solveNQueens(n);
cout << ret.size() << endl;
for (int i = 0; i < ret.size(); ++i) {
for (int j = 0; j < n * n; j++) {
cout << " " << ret[i][j] << " ";
}
cout << endl;
}
return 0;
}