240. Search a 2D Matrix II

Posted 2020-09-22

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 in ascending from left to right.
• Integers in each column are sorted in ascending from top to bottom.

 

For example,

Consider the following 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]
]

Given target = 5, return true.

Given target = 20, return false.

 

 

 

class Solution {
public:
bool searchMatrix(vector<vector<int>>& matrix, int target) {
if (matrix.size() == 0 || matrix[0].size() ==0 ) {
return false;
}

int i = 0, j = matrix[0].size() -1;
while (i < matrix.size() && j >= 0) {
if (matrix[i][j] == target) {
return true;
} else if (matrix[i][j] < target) {
i++;
} else {
j--;
}
}

return false;
}
};