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. Constraints n ≤ 100,000 where n is the length of nums Example 1 Input nums = [2, 0, 2] target = 2 Output 4 Explanation 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];
mp[sum]++;
}
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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