AcWing 143. 最大异或对

143最大异或对.cc

#include <iostream>
#include <vector>
#include <array>

using namespace std;

class TrieTree {
public:
    TrieTree() : nodeSize(1) { }
    
    void insert(int num) {
        int currNodeIndex = 0;
        for (int digit = 30; digit >= 0; digit--) {
            int bit = (num >> digit) & 1;
            
            /* node does not exist */
            if (nodes[currNodeIndex][bit] == 0) {
                nodeSize++;
                nodes[currNodeIndex][bit] = nodeSize-1;
            }
            
            /* jump to next node */
            currNodeIndex = nodes[currNodeIndex][bit];
        }
    }
    
    int query(int num) {
        int ans = 0;
        
        int currNodeIndex = 0;
        for (int i = 30; i >= 0; i--) {
            int bit = (num >> i) & 1;
            
            if (nodes[currNodeIndex][!bit] != 0) {
                ans += (1 << i);
                currNodeIndex = nodes[currNodeIndex][!bit];
            } else {
                currNodeIndex = nodes[currNodeIndex][bit];
            }
        }
        
        return ans;
    }


private:
    array<array<int, 2>, static_cast<long unsigned int>(32*(1e5))> nodes;
    int nodeSize = 0;
    
};

int main()
{
    int N;
    TrieTree trie;
    vector<int> nums;

    cin >> N;
    
    int num;
    for (int i = 0; i < N; i++) {
        cin >> num;
        nums.push_back(num);
        trie.insert(num);
    }
    
    int ans = 0;
    for (auto val : nums) {
        ans = max(ans, trie.query(val));
    }
    
    cout << ans;

    
    return 0;
}