240. Search a 2d Matrix II

Problem Statement

Medium

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

Java

Source file

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