[LeetCode 240] Search a 2D matrix II

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本文介绍了一种高效的算法，用于在一个特殊结构的矩阵中查找特定值。该矩阵每一行及每一列都按升序排列。文章提供了一个具体的例子并附带了实现该算法的Java代码。

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:

search from matrix right top element, if smaller than target go left, if larger than target, go down.

met this in Microsoft interview last year.

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