# 240.Search a 2D Matrix II

## August 15, 2016

240.Search a 2D Matrix II

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.

/*solution1 264ms*/
class Solution {
public:
bool searchMatrix(vector<vector<int>>& matrix, int target) {
if(matrix.empty()||matrix[0].empty())
return false;
int row=0,col=matrix[0].size()-1,size=matrix.size();
while(row<size&&col>=0){
if(matrix[row][col]==target)
return true;
else if(matrix[row][col]>target)
col--;
else if(matrix[row][col]<target)
row++;
}
return false;
}
};


/*solution2 164ms*/
class Solution {
public:
bool searchMatrix(vector<vector<int>>& matrix, int target) {
int row = matrix.size();
int col = matrix[0].size();
int i = row-1,j =0;
while(i>=0&&j<col){
if(target>matrix[i][j])
j++;
else if(target<matrix[i][j])
i--;
else
return true;
}
return false;
}
};


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