[leedcode 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.

public class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        //没有搞清楚和Search a 2D Matrix 的区别？？？
        if(matrix.length<=0) return false;
        int row=matrix.length;
        int col=matrix[0].length;
        int i=0;
        int j=col-1;
        while(i<row&&j>=0){
            if(matrix[i][j]==target) return true;
            if(matrix[i][j]>target){
                j--;
            }else{
                i++;
            }
        }
        return false;
    }
}