Leetcode Two sum problem

Source: Dev.to

Two Sum

Working

• seen keeps track of numbers we’ve already visited and their indices.
• For each num, we calculate complement = target - num.
• If the complement is already in seen, we return the pair of indices.
• Otherwise, we store the current number with its index.

Two Sum II – Input Array Is Sorted

Working

• Start with two pointers left at the beginning and right at the end.
• Compute the sum of the two numbers.
• If the sum equals the target, return their indices.
• If the sum is too small, move left forward to increase the sum.
• If the sum is too large, move right backward to decrease the sum.