[leetcode-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.

思路：

二分查找。将矩阵看成是一维的，索引为

matrix[middle / col][middle%col]

bool searchMatrix(vector<vector<int>>& matrix, int target)
     {
         if (matrix.size() == 0) return false;
        
         int row = matrix.size(), col = matrix[0].size();
         int left = 0, right = row*col - 1, middle = left + (right - left) / 2;
         
         while (left <= right)
         {
             middle = left + (right - left) / 2;
             if (target == matrix[middle / col][middle%col])return true;
             else if (target < matrix[middle / col][middle%col])right = middle - 1;
             else left = middle + 1;
         }
         return false;         
     }