LeetCode: Search a 2D Matrix

Search a 2D Matrix

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 from left to right.
• The first integer of each row is greater than the last integer of the previous row.

For example,

Consider the following matrix:

[
  [1,   3,  5,  7],
  [10, 11, 16, 20],
  [23, 30, 34, 50]
]

Given target = 3, return true.

public class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        // Start typing your Java solution below
        // DO NOT write main() function
        if(matrix==null || matrix.length==0 || matrix[0].length==0) 
            return false;
        int start = 0, end = matrix.length*matrix[0].length-1;
        
        while(start<=end){
            int mid=(start+end)/2, midX=mid/matrix[0].length,
                midY=mid%matrix[0].length;
            if(matrix[midX][midY]==target) return true;
            if(matrix[midX][midY]<target){
                start=mid+1;
            }else{
                end=mid-1;
            }
        }
        return false;
    }
}