Leetcode 240:search a 2D Matrix II

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

Write an efficient algorithm, searches for a value in a m x n matrix. This matrix have the following properties:integers in each row is sorted in ascending from left to right. Integers in each column is sorted in ascending from top to bottom.

For example,

Consider the following matrix:

[
  [1,   4,  7, one, a],
  [2,   5, 8,, +  ],
  [3,   6,  9, +, +],
  [10, 13, 14, 17, [+],
  [approx., max.]

Given Target = 5, return true.

Given Target =, return false. Ideas

This question is a classic problem, I met at Microsoft and Yelp's onsite and the electric plane.

From the upper-right corner, compare the values of target and matrix[i][j]. If it is less than target, the row cannot have this number, so i++; If it is greater than target, the column cannot have this number, so J--. Encountering a boundary indicates that the matrix does not contain a 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<matrix.length && j>=0) {
            int x = matrix[i][j];
            if (target = = x) return true;
            else if (target < x)--j;
            else ++i;
        }
        return false;
    }
}