src/main/java/com/fishercoder/solutions/_36.java

package com.fishercoder.solutions;

public class _36 {

    public static class Solution1 {
        public boolean isValidSudoku(char[][] board) {
            for (int i = 0; i < 9; i++) {
                if (!isValidRowOrColumn(board, i)) {
                    return false;
                }
            }

            for (int j = 0; j < 9; j++) {
                if (!isValidCol(board, j)) {
                    return false;
                }
            }

            for (int i = 0; i < 7; i = i + 3) {
                for (int j = 0; j < 7; j = j + 3) {
                    if (!isValidSquare(board, i, j)) {
                        return false;
                    }
                }
            }
            return true;
        }

        boolean isValidRowOrColumn(char[][] board, int index) {
            int[] nums = new int[9];
            for (int i = 0; i < 9; i++) {
                nums[i] = 1;
            }
            for (int j = 0; j < 9; j++) {
                if (board[index][j] != '.') {
                    nums[Character.getNumericValue(board[index][j]) - 1]--;
                }
            }
            for (int i : nums) {
                if (i < 0) {
                    return false;
                }
            }
            return true;
        }

        boolean isValidCol(char[][] board, int col) {
            int[] nums = new int[9];
            for (int i = 0; i < 9; i++) {
                nums[i] = 1;
            }
            for (int i = 0; i < 9; i++) {
                if (board[i][col] != '.') {
                    nums[Character.getNumericValue(board[i][col]) - 1]--;
                }
            }
            for (int i : nums) {
                if (i < 0) {
                    return false;
                }
            }
            return true;
        }

        boolean isValidSquare(char[][] board, int row, int col) {
            int[] nums = new int[9];
            for (int i = 0; i < 9; i++) {
                nums[i] = 1;
            }
            for (int i = row; i < row + 3; i++) {
                for (int j = col; j < col + 3; j++) {
                    if (board[i][j] != '.') {
                        nums[Character.getNumericValue(board[i][j]) - 1]--;
                    }
                }
            }
            for (int i : nums) {
                if (i < 0) {
                    return false;
                }
            }
            return true;
        }
    }
}