74. Search a 2D Matrix
Difficulty: Medium
Topics: Array, Binary Search
Similar Questions:
Problem:
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.
Example 1:
Input: matrix = [ [1, 3, 5, 7], [10, 11, 16, 20], [23, 30, 34, 50] ] target = 3 Output: true
Example 2:
Input: matrix = [ [1, 3, 5, 7], [10, 11, 16, 20], [23, 30, 34, 50] ] target = 13 Output: false
Solutions:
class Solution {
public:
bool searchMatrix(vector<vector<int>>& matrix, int target) {
int m = matrix.size();
if (m == 0) return false;
int n = matrix[0].size();
if (n == 0) return false;
int left = 0;
int right = m * n - 1;
while (left <= right) {
int mid = left + (right - left) / 2;
auto coord = arrayToMatrix(m, n, mid);
int row = coord.first;
int col = coord.second;
if (matrix[row][col] == target) return true;
if (matrix[row][col] > target) {
right = mid - 1;
} else {
left = mid + 1;
}
}
return false;
}
inline pair<int, int> arrayToMatrix(int m, int n, int index) {
return {index/n, index%n};
}
};