240. Search a 2D Matrix II Leetcode java Solution

Write an efficient algorithm that searches for a value target in an m x n integer matrix 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.

Example 1

Input: 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]], target = 5
Output: true

Example 2 

Input: 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]], target = 20
Output: false

Constraints

• m == matrix.length
• n == matrix[i].length
• 1 <= n, m <= 300
• -10⁹ <= matrix[i][j] <= 10⁹
• All the integers in each row are sorted in ascending order.
• All the integers in each column are sorted in ascending order.
• -10⁹ <= target <= 10⁹

Solution

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