Leetcode 240: Search a 2D Matrix II

Leetcode 240: Search a 2D Matrix II

 

Search a 2D Matrix IITotal Accepted: 520Total Submissions: 1659

 

Write an efficient algorithm that searches for a value inMXNMatrix. 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]]

GivenTarget=5, Returntrue.

GivenTarget=20, Returnfalse.

[Idea]

This is a classic question. I met both the onsite and the electrical interface of Microsoft and YELP.

Compare the values of target and matrix [I] [j] from the upper right corner. if the value is smaller than the target value, the row cannot have this number, so I ++; if the value is greater than the target value, this column cannot have this number, so j --. if a boundary exists, the matrix does not contain the target.

[CODE]

 

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