Search a 2D matrix II Leetcode Solution
Search a 2D matrix II Leetcode Problem :
Write an efficient algorithm that searches for a value target in an m x n integer matrix matrix. This matrix has the following properties:
- Integers in each row are sorted in ascending from left to right.
- Integers in each column are sorted in ascending from top to bottom.
Example :
Input: matrix = [[1,4,7,11,15],[2,5,8,12,19],[3,6,9,16,22],[10,13,14,17,24],[18,21,23,26,30]],
target = 5
Output: true
Search a 2D Matrix || Leetcode Solution :
Constraints :
- m == matrix.length
- n == matrix[i].length
- 1 <= n, m <= 300
- -109 <= matrix[i][j] <= 109
- All the integers in each row are sorted in ascending order.
- All the integers in each column are sorted in ascending order.
- -109 <= target <= 109
Example 1:
- Input: matrix = [[1,4,7,11,15],[2,5,8,12,19],[3,6,9,16,22],[10,13,14,17,24],[18,21,23,26,30]], target = 20
- Output: false
Intuition :
Traversing using corner elemnts;
Approach :
- first choose the corner (either top right or bottom left)….i have chosen bottom left
- Traverse till opposite corner is reaches..
- a) if corner element is equal to target ….return true;
b) if target is smaller than corner elemnt….then the target must be abbove the bottom row…..so bottom row–;
c) if target is greater than corner elemnt….then the target must be on the rigth of left column…..so left column++; - if loop completes means no element found so return false.
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Code :
C++
Java
Python
C++
class Solution {
public:
bool searchMatrix(vector< vector< int>>& matrix, int target) {
int n=matrix.size();
int m=matrix[0].size();
int i=0,j=m-1;
while(i< n && j>=0)
{
if(matrix[i][j]==target)
return true;
else if(matrix[i][j]>target)
j--;
else
i++;
}
return false;
}
};
Java
class Solution {
public boolean searchMatrix(int[][] matrix, int target) {
int r = matrix.length;
int c = matrix[0].length;
int b = c-1;
int l = 0;
while(l=0){
if(matrix[l][b]==target){
return true;
}
else if(matrix[l][b]>target){
b--;
}
else{
l++;
}
}
return false;
}
}
Python
class Solution:
def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
ROWS, COLS = len(matrix), len(matrix[0])
for row in range(ROWS):
if matrix[row][0] <= target and matrix[row][-1] >= target:
top, bot = 0, COLS
while top < bot:
mid = (top + bot) // 2
if target > matrix[row][mid]:
top = mid + 1
elif target < matrix[row][mid]:
bot = mid
else:
return True
return False
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