September 17Medium

Find two non overlapping sub arrays each with target sum

Array
Hash Table
Binary Search
Dynamic Programming
Sliding Window

Problem

You are given an array of integers arr and an integer target.

You have to find two non-overlapping sub-arrays of arr each with a sum equal target. There can be multiple answers so you have to find an answer where the sum of the lengths of the two sub-arrays is minimum.

Return the minimum sum of the lengths of the two required sub-arrays, or return -1 if you cannot find such two sub-arrays.

Solution

class Solution:
    def minSumOfLengths(self, arr: list[int], target: int) -> int:
        n = len(arr)
        suffix = [float("inf")] * (n + 1)
        end = n - 1
        curr_sum = 0
        for start in range(n-1, -1, -1):
            curr_sum += arr[start]
            while curr_sum > target:
                curr_sum -= arr[end]
                end -= 1
            if curr_sum == target:
                length = end - start + 1
                suffix[start] = min(length, suffix[start + 1])
            else:
                suffix[start] = suffix[start + 1] 

        curr_sum = 0
        start = 0
        res = float("inf")
        for j in range(n):
            curr_sum += arr[j]
            while curr_sum > target:
                curr_sum -= arr[start]
                start += 1
            if curr_sum == target:
                res = min(res, j - start + 1 + suffix[j + 1])

        return res if res != float("inf") else -1