DEV Community: Jayesh Adwani

Find all unique triplets that sum upto 0

Jayesh Adwani — Wed, 20 Aug 2025 04:03:04 +0000

Initially I struggled to find the right approach to the problem. I used 3 pointers thought it would save the performance cases. But I was wrong there, this is a two pointer problem after sorting.

Approach: for an index i, take j and k such that, arr[i] + arr[j] +arr[k] equals 0.
If sum < 0, j++,
If sum > 0, k--,
If sum = 0, j++, k--,

Handle duplicates for i,j,k by comparing current to next index elements

Try all combinations using while loop inside a for loop

Time Complexity: O(nlogn) + O(n*m) where m is elements from next to last element.

Space Complexity: O(n)

[Boost]

Jayesh Adwani — Wed, 20 Aug 2025 03:52:46 +0000

Move all the zeros to the right of the array.

Jayesh Adwani — Mon, 18 Aug 2025 19:20:00 +0000

Array contains 0 and positive numbers.

Approach 1: Brute force, iterate over array if element is 0, find the next non-zero element to swap, using while loop.

Good, solves the issue but failed performance test cases. As nested loops are used.

Time Complexity: O(n*m), where m is number of elements to the right of current element.
Space Complexity: O(1), no memory resource utilized.

Approach 2; To obtain result in single loop, create a new array vector the first push the non-zero elements then remaining zeros.

Passed all the test cases

Time Complexity: O(n)
Space Complexity: O(n)