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-rw-r--r--transform_to_chessboard.c57
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diff --git a/transform_to_chessboard.c b/transform_to_chessboard.c
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+// 782. Transform to Chessboard
+#include "leetcode.h"
+
+/*
+ * you are given an 'n * n' binary grid 'board'. in each move, you can swap any
+ * two rows with each other, or any two columns with each other. return the
+ * minimum number of rwos to transform the board intoa chessboard board. if the
+ * task is impossible, return -1. a chessboard board is a board where no 0's and
+ * no 1's are 4-directionally adjacent
+ */
+
+int movesToChessboard(int **board, int boardSize, int *boardColSize) {
+ int n = boardSize, row_sum = 0, col_sum = 0, row_swap = 0, col_swap = 0;
+ for (int i = 0; i < n; ++i)
+ for (int j = 0; j < n; ++j)
+ if (board[0][0] ^ board[i][0] ^ board[0][j] ^ board[i][j])
+ return -1;
+ for (int i = 0; i < n; ++i) {
+ row_sum += board[0][i];
+ col_sum += board[i][0];
+ row_swap += board[i][0] == i % 2;
+ col_swap += board[0][i] == i % 2;
+ }
+ if (row_sum != n / 2 && row_sum != (n + 1) / 2)
+ return -1;
+ if (col_sum != n / 2 && col_sum != (n + 1) / 2)
+ return -1;
+ if (n % 2) {
+ if (col_swap % 2)
+ col_swap = n - col_swap;
+ if (row_swap % 2)
+ row_swap = n - row_swap;
+ } else {
+ col_swap = fmin(n - col_swap, col_swap);
+ row_swap = fmin(n - row_swap, row_swap);
+ }
+ return (col_swap + row_swap) / 2;
+}
+
+int main() {
+ int b1i[4][4] = {{0, 1, 1, 0}, {0, 1, 1, 0}, {1, 0, 0, 1}, {1, 0, 0, 1}};
+ int b2i[2][2] = {{0, 1}, {1, 0}};
+ int b3i[2][2] = {{1, 0}, {1, 0}};
+ struct two_d_arr b1, b2, b3;
+ two_d_arr_init(&b1, 4, 4, b1i);
+ two_d_arr_init(&b2, 2, 2, b2i);
+ two_d_arr_init(&b3, 2, 2, b3i);
+ printf("%d\n",
+ movesToChessboard(b1.arr, b2.row_size, b3.col_size)); // expect: 2
+ printf("%d\n",
+ movesToChessboard(b2.arr, b2.row_size, b2.col_size)); // expect: 0
+ printf("%d\n",
+ movesToChessboard(b3.arr, b3.row_size, b3.col_size)); // expect: -1
+ two_d_arr_free(&b1);
+ two_d_arr_free(&b2);
+ two_d_arr_free(&b3);
+}