Leetcode 240:search a 2D Matrix II

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

Write an efficient algorithm, searches for a value in a m x n Matrix. This matrix has 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, A, 3],  [6,   9,, +, +  ],  [10, 13, 14, ,  [18, 21, 23, 26, 30]]

Given Target = 5 , return true .

Given Target = 20 , 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;    }}

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Leetcode 240:search a 2D Matrix II