## Search A 2D Matrix

06/28/2016 Array Binary Search

## Question

Write an efficient algorithm that searches for a value in an $m*n$ 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.

For example, Consider the following matrix:

[
[1,   3,  5,  7],
[10, 11, 16, 20],
[23, 30, 34, 50]
]


Given $target$ = 3, return true.

## Solution

Result: Accepted Time: 8 ms

Here should be some explanations.

bool searchMatrix(int** matrix, int matrixRowSize, int matrixColSize, int target) {
register int dx = matrixRowSize - 1,dy = 0,tmp,tar=target;
while(dy < matrixColSize && dx >= 0)
{
tmp = matrix[dx][dy];
if(tar == tmp) return true;
if(tar > tmp)
++dy;
else
--dx;
}
return false;
}


Complexity Analytics

• Time Complexity: $O(n)$
• Space Complexity: $O(1)$