[3] Give an efficient algorithm to rearrange an array of n keys so that all the negative keys precede all the nonnegative keys.

Give an efficient algorithm to rearrange an array of n keys so that all the
negative keys precede all the nonnegative keys.

 

Solution:

1. Scan through the list from left to right through i .

2. Point the first positive number in the list say it  j (initially -1).

3. When List[i] is a negative number and j >-1, swap list[i] & list [j] and increment j by 1

4. When List[i] is a negative number and j == -1, we haven’t get any positive number and go through scanning.

 

Complexity : O(n)

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