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

.

class Solution {
public:
bool searchMatrix(vector<vector<int> > &matrix, int target) {
int sizeX = (int)matrix.size();
if (0 == sizeX)
{
return false;
}
int sizeY = (int)matrix[0].size();
return searchMatrix(matrix, target, 0, 0, sizeX - 1, sizeY - 1);
}
private:
bool searchMatrix(vector<vector<int> > &matrix, int target, int begX, int begY, int endX, int endY)
{
if (begX > endX || begY > endY)
{
return false;
}
int midX = (begX + endX) >> 1;
int midY = (begY + endY) >> 1;
vector<int> const & tmp = matrix[midX];
int val = tmp[midY];
if (val == target)
{
return true;
}
if (target > val)
{
if (target > tmp[endY])
{
return searchMatrix(matrix, target, midX + 1, begY, endX, endY);
}
return binary_search(&tmp[midY], &tmp[endY] + 1, target);
}
if (target < tmp[begY])
{
return searchMatrix(matrix, target, begX, begY, midX - 1, endY);
}

return binary_search(&tmp[begY], &tmp[midY], target);
}
};