Searcha2DMatrix.java

package leetcode;

/**
 * @author eko
 * @date 2018/10/24 9:28 AM
 *
 * Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:
 *
 * Integers in each row are sorted from left to right.
 * The first integer of each row is greater than the last integer of the previous row.
 * Example 1:
 *
 * Input:
 * matrix = [
 *   [1,   3,  5,  7],
 *   [10, 11, 16, 20],
 *   [23, 30, 34, 50]
 * ]
 * target = 3
 * Output: true
 * Example 2:
 *
 * Input:
 * matrix = [
 *   [1,   3,  5,  7],
 *   [10, 11, 16, 20],
 *   [23, 30, 34, 50]
 * ]
 * target = 13
 * Output: false
 */
public class Searcha2DMatrix {
    public static void main(String[] args) {
        int[][] matrix = {
                {1, 3, 5, 7},
                {10, 11, 16, 20},
                {23, 30, 34, 50}
        };
        int target = 3;
        boolean res = new Searcha2DMatrix().searchMatrix(matrix, target);
        System.out.println(res);
    }

    public boolean searchMatrix(int[][] matrix, int target) {
        if (matrix.length < 1 || matrix[0].length < 1) return false;
        int row = 0;
        int col = matrix[0].length - 1;
        while (col >= 0 && row < matrix.length) {
            if (matrix[row][col] == target) return true;
            else if (target < matrix[row][col]) col--;
            else row++;
        }
        return false;
    }
}