Update Day10/N-Queens.cpp

muditmahajan21 · May 23, 2022 · e84ac66 · e84ac66
1 parent 0b085f0
commit e84ac66
Showing 1 changed file with 36 additions and 0 deletions.
diff --git a/Day10/N-Queens.cpp b/Day10/N-Queens.cpp
@@ -0,0 +1,36 @@
+void solve(int col, vector<string> &board, vector<vector<string>> &ans, vector<bool> &left_row, vector<bool> &upper_diag, vector<bool> &lower_diag, int n) {
+        if(col == n) {
+            ans.push_back(board);
+            return;
+        }
+
+        for(int row = 0; row < n; row++) {
+            if(!left_row[row] and !upper_diag[n - 1 + col - row] and !lower_diag[col + row]) {
+                board[row][col] = 'Q';
+                left_row[row] = true;
+                upper_diag[n - 1 + col - row] = true;
+                lower_diag[col + row] = true;
+
+                solve(col + 1, board, ans, left_row, upper_diag, lower_diag, n);
+
+                board[row][col] = '.';
+                left_row[row] = false;
+                upper_diag[n - 1 + col - row] = false;
+                lower_diag[col + row] = false;
+            }
+        }
+     }
+
+    vector<vector<string>> solveNQueens(int n) {
+        vector<vector<string>> ans;
+        vector<string> board(n);
+        string s(n, '.');
+
+        for(int i = 0; i < n; i++) {
+            board[i] = s;
+        }
+
+        vector<bool> left_row(n, false), upper_diag(2 * n - 1, false), lower_diag(2 * n - 1, false);
+        solve(0, board, ans, left_row, upper_diag, lower_diag, n);
+        return ans;
+    }