[LeetCode 240] Search a 2D matrix II

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;    }