2275. Largest Combination With Bitwise AND Greater Than Zero

MediumView on LeetCode

Array Hash Table Bit Manipulation Counting enumeration

Time: O(n * 24)

Space: O(1)

Intuition

Count values that have all required bits set (value & bits == bits). For each candidate in votes, check bitmask.

Algorithm

1For each candidate: if (candidate & bits) == bits: count++.

Common Pitfalls

•All bits in the required mask must be set. Use bitwise AND.

2275.cs

// Approach: For each bit position count how many candidates have that bit set; return max count.
// Time: O(n * 24) Space: O(1)

public class Solution
{
    public int LargestCombination(int[] candidates)
    {
        const int kMaxBit = 24;
        int ans = 0;

        for (int i = 0; i < kMaxBit; ++i)
        {
            int count = 0;
            foreach (var candidate in candidates)
            {
                if ((candidate >> i & 1) == 1)
                    ++count;
            }
            ans = Math.Max(ans, count);
        }

        return ans;
    }
}

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