Search a 2D Matrix
Write an efficient algorithm that searches for a value in anm 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) {
if (matrix.empty()) return false;
int m = matrix.size();
int n = matrix[0].size();
int first = 0;
int last = m*n;
while (first < last) {
int mid = first + (last - first) /2;
int value = matrix[mid /n][mid %n];
if(value == target)
return true;
else if (value < target)
first = mid +1;
else
last = mid;
}
return false;
}
};
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