Number of Sublists With Sum of Target - Amazon Top Interview Questions

Problem Statement :

Given a list of integers nums and an integer target, return the number of sublists whose sum is equal to target.


n ≤ 100,000 where n is the length of nums

Example 1


nums = [2, 0, 2]
target = 2




We have these sublists whose sum is 2: [2], [2, 0], [0, 2], [2]

Solution :


                        Solution in C++ :

int solve(vector<int>& nums, int k) {
    int count = 0, sum = 0;
    unordered_map<int, int> mp;
    for (int i = 0; i < nums.size(); i++) {
        sum += nums[i];
        if (sum == k) count++;
        count += mp[sum - k];
    return count;

                        Solution in Python : 
class Solution:
    def solve(self, nums, target):
        prefix_table = {0: 1}
        prefix_sum = 0
        count = 0

        for n in nums:
            prefix_sum += n
            # Is there a prefix we can remove in the subarray window that will add to the target?
            # if so - add the total
            if prefix_sum - target in prefix_table:
                count += prefix_table[prefix_sum - target]
            prefix_table[prefix_sum] = (
                prefix_table[prefix_sum] + 1 if prefix_sum in prefix_table else 1
        return count

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