240. Search a 2D Matrix II

Search a 2D Matrix II

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 in ascending from left to right. Integers in each column are sorted in ascending from top to bottom.

For example,

Consider the following matrix:

[ [1, 4, 7, 11, 15], [2, 5, 8, 12, 19], [3, 6, 9, 16, 22], [10, 13, 14, 17, 24], [18, 21, 23, 26, 30] ]

Given target = 5, return true. Given target = 20, return false.

Solution

public class Solution {
 public boolean searchMatrix(int[][] matrix, int target) {
        if (matrix == null || matrix.length == 0) return false;

        int row = matrix.length;
        int column = matrix[0].length;

        if (column == 0) {
            return false;
        }

        int x = row - 1;
        int y = 0;
        while (x >= 0 && y <= column - 1) {
            if (matrix[x][y] == target) return true;
            else if (matrix[x][y] < target) {
                y++;
            } else {
                x--;
            }
        }

        return false;
    }
}