Problem: Two Sum

For the given array of integers arr and a target t, you have to identify the two indices that add up to generate the target t. Moreover, you can’t use the same index twice, and there will be only one solution.

Note: We will assume that the array is zero-indexed and the output order doesn’t matter.

Constraints:

• $2 \leq$ arr.length $\leq 10^3$
• $-10^9 \leq$ arr[i] $\leq 10^9$
• $-10^9 \leq$ t $\leq 10^9$
• Only one valid answer exists.