Thinking
The array features can start searching at the top right or bottom left corner of the element, if not equal to the target, it can be directly reduced in a row or lookup.
Code
Time complexity: O (n + m)
Complexity Space: O (1)
class Solution {
public:
bool findNumberIn2DArray(vector<vector<int>>& matrix, int target) {
if (matrix.empty()) return false;
int row = matrix.size(), col = matrix[0].size();
int i = row - 1, j = 0;
while (i >= 0 && j < col) {
if (target == matrix[i][j]) return true;
else if (target < matrix[i][j]) --i;
else ++j;
}
return false;
}
};
Another way
class Solution {
public:
bool findNumberIn2DArray(vector<vector<int>>& matrix, int target) {
if (matrix.empty()) return false;
int row = matrix.size(), col = matrix[0].size();
int i = 0, j = col - 1;
while (i < row && j >= 0) {
if (target == matrix[i][j]) return true;
else if (target < matrix[i][j]) --j;
else ++i;
}
return false;
}
};