74. 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.

一刷
题解：
将多维矩阵视为一维

public class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        if(matrix == null || matrix.length == 0) return false;
        int n = matrix.length, m = matrix[0].length;
        int lo = 0;
        int hi = m*n - 1;
        while(hi>=lo){
            int mid = lo + (hi - lo)/2;
            int num = matrix[mid/m][mid%m];
            if( num == target) return true;
            else if(num < target) lo = mid+1;
            else hi = mid-1;
        }
        
        return false;
    }
}