LeetCode74 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. （Medium）

分析：

考察题目给的二维数组的特点发现，其本质跟一个排好序的一维数组没有区别，所以就是一个二分查找问题。

对于mid，其对应的点是matrix[mid / n][mid % n]

代码：

 class Solution {
 public:
     bool searchMatrix(vector<vector<int>>& matrix, int target) {
         int m = matrix.size(), n = matrix[].size();
         int start = , end = m * n - ;
         while (start +  < end) {
             int mid = start + (end - start) / ;
             if (matrix[mid / n][mid % n] == target) {
                 return true;
             }
             else if (matrix[mid / n][mid % n] < target) {
                 start = mid;
             }
             else {
                 end = mid;
             }
         }
         if (matrix[start / n][start % n] == target) {
             return true;
         }
         if (matrix[end / n][end % n] == target) {
             return true;
         }
         return false;
     }
 };