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.

C++:
01 class Solution {
02 public:
03     bool searchMatrix(vector<vector<int> > &matrix, int target) {
04         // Start typing your C/C++ solution below
05         // DO NOT write int main() function
06         int n=matrix.size();
07         if(n==0)
08             return false;
09         int m=matrix[0].size();
10         int x=0;
11         int y=n1;
12         while((x<m)&&(y>=0))
13         {
14             if(matrix[y][x]==target)
15                 return true;
16             if(matrix[y][x]<target)
17                 x++;
18             else
19                 y;
20         }
21         return false;
22     }
23 };
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