Link: https://leetcode.cn/problems/search-a-2d-matrix-ii/

Question

difficulty: mid
adj diff: 2

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

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Code

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public boolean searchMatrix(int[][] matrix, int target) {
    int m = matrix.length;
    int n = matrix[0].length;
    int x = m - 1;
    int y = 0;

    while (x >= 0 && y < n) {
        if (matrix[x][y] == target) {
            return true;
        } else if (matrix[x][y] > target) {
            x--;
        } else if (matrix[x][y] < target) {
            y++;
        }
    }
    return false;
}