BOJ 29441 : XOR

• 문제 링크 : boj.kr/29441
• 난이도 : P3
• 태그 : 트라이

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코드

#include <bits/stdc++.h>

#define all(x) (x).begin(), (x).end()

#define INF 0x7FFFFFFF

using namespace std;

using ll = long long;
using ld = long double;
using pii = pair<int,int>;
using pll = pair<ll, ll>;

class Trie {
public:
    Trie* children[2];
    bool end;

    Trie() : end(false) {children[0] = children[1] = NULL;}

    void insert(vector<int>& key) {
        this->_insert(key, 0);
    };
    int find(vector<int>& key) {
        return this->_find(key, 0, 0);
    };

private:
    void _insert(vector<int>& key, int index) {
        if(index == key.size()) {
            end = true;
            return;
        }
        int next = key[index];
        if(children[next] == NULL) children[next] = new Trie();
        children[next]->_insert(key, index + 1);
    }
    int _find(vector<int>& key, int depth, int num) {
        int ret;
        int next = key[depth];
        if(children[!next] == NULL) ret = next;
        else {
            ret = !next;
            next = !next;
        }
        if(depth == key.size()) return num;
        return children[next]->_find(key, depth + 1, num*2 + ret);
    }
};

vector<int> int_to_bits(int num) {
    vector<int> temp(31);
    bitset<31> bs(num);
    for(int i = 0; i < 31; i++) {
        temp[i] = bs[30-i];
    }
    return temp;
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    Trie root;

    int n;
    cin >> n;
    for(int i = 0; i < n; i++) {
        int input;
        cin >> input;
        vector<int> arr = int_to_bits(input);
        root.insert(arr);
    }
    int m;
    cin >> m;
    for(int i = 0; i < m; i++) {
        int input;
        cin >> input;
        vector<int> arr = int_to_bits(input);
        cout << root.find(arr) << " ";
    }

    return 0;
}

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풀이

트라이를 이용해 XOR최댓값을 찾아준다.