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.

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.

方法1：

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

時間複雜度：O(n)

空間複雜度：O(1)

原始碼github地址：https://github.com/zhangyu345293721/leetcode