How hard is LeetCode 1711. Count Good Meals?

LeetCode 1711. Count Good Meals is rated Medium on LeetCode.

What is the time complexity of LeetCode 1711. Count Good Meals?

The Python solution on this page runs in O(n \times \log M), where n is the length of the array `deliciousness`, and M is the upper limit of the elements.

What is the space complexity of LeetCode 1711. Count Good Meals?

The Python solution on this page uses O(n) auxiliary space.

What topics does LeetCode 1711. Count Good Meals cover?

LeetCode 1711. Count Good Meals is tagged Array and Hash Table on LeetCode.

Count Good Meals — LeetCode 1711 Python Solution

MediumArrayHash Table

Problem: #1711
Pattern: Hash Map
Reading time: 2 min
Source: leetcode.com

The problem

A good meal is a meal that contains exactly two different food items with a sum of deliciousness equal to a power of two. You can pick any two different foods to make a good meal.

Example

Input: deliciousness = [1,3,5,7,9]
Output: 4
Explanation: The good meals are (1,3), (1,7), (3,5) and, (7,9).

Python solution

Python

class Solution:
    def countPairs(self, deliciousness: List[int]) -> int:
        mod = 10**9 + 7
        mx = max(deliciousness) << 1
        cnt = Counter()
        ans = 0
        for d in deliciousness:
            s = 1
            while s <= mx:
                ans = (ans + cnt[s - d]) % mod
                s <<= 1
            cnt[d] += 1
        return ans

Complexity

Measure	Complexity
Time	O(n \times \log M), where n is the length of the array `deliciousness`, and M is the upper limit of the elements
Space	O(n) auxiliary

Pattern: Hash Map

Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 1711. Count Good Meals is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Hash Table.

The hash map guide has the Python template for the pattern and the 709 LeetCode problems that use it.

Frequently asked questions

How hard is LeetCode 1711. Count Good Meals?: LeetCode 1711. Count Good Meals is rated Medium on LeetCode.
What is the time complexity of LeetCode 1711. Count Good Meals?: The Python solution on this page runs in O(n \times \log M), where n is the length of the array `deliciousness`, and M is the upper limit of the elements.
What is the space complexity of LeetCode 1711. Count Good Meals?: The Python solution on this page uses O(n) auxiliary space.
What topics does LeetCode 1711. Count Good Meals cover?: LeetCode 1711. Count Good Meals is tagged Array and Hash Table on LeetCode.