Add 52 in c language

c/52-n-queens-ii.c

@@ -0,0 +1,53 @@
+/*
+Given an integer n, return the number of distinct solutions to the n-queens puzzle.
+
+Space: O(n²)
+Time: ?
+*/
+
+int min(int a, int b){
+ return a<b?a:b;
+}
+
+int can_ce_placed(int i, int j, int n, int** board) {
+ for (int k=i-1; k>=0; k--)
+ if (board[k][j])
+ return false;
+ for (int k=j-1; k>=0; k--)
+ if (board[i][k])
+ return false;
+ int m = min(i, j)+1;
+ for (int k=1; k<m; k++)
+ if (board[i-k][j-k])
+ return false;
+ m = min(i+1, n-j);
+ for (int k=1; k<m; k++)
+ if (board[i-k][j+k])
+ return false;
+ return true;
+}
+
+int backtracking(int i, int n, int** board) {
+ if (i==n)
+ return 1;
+ int cpt = 0;
+ for (int k=0; k<n; k++){
+ if (can_ce_placed(i, k, n, board)){
+ board[i][k] = 1;
+ cpt += backtracking(i+1, n, board);
+ board[i][k] = 0;
+ }
+ }
+ return cpt;
+}
+
+int totalNQueens(int n){
+ int** board = malloc(sizeof(int*)*n);
+ for (int i=0; i<n; i++)
+ board[i] = calloc(n, sizeof(int));
+ int ans = backtracking(0, n, board);
+ for (int i=0; i<n; i++)
+ free(board[i]);
+ free(board);
+ return ans;
+}