LeetCode 数组中两个数的最大异或值

题目链接：https://leetcode-cn.com/problems/maximum-xor-of-two-numbers-in-an-array/

题目大意：

　　略。

分析：

　　字典树 + 贪心.

代码如下：

 class Trie {
 public:
     int passed; // 记录经过这个节点的字符串数量
     int ends;   // 记录有多少个字符串以这个节点结尾
     Trie* nxt[];

     /** Initialize your data structure here. */
     Trie() {
         passed = ;
         ends = ;
         nxt[] = nxt[] = NULL;
     }

     /** Inserts a word into the trie. */
     void insert(string word) {
         Trie* p = this;
         for(int i = ; i < word.size(); ++i) {
             int key = word[i] - '';

             if(p->nxt[key] == NULL) {
                 p->nxt[key] = new Trie();
             }
             ++p->passed;
             p = p->nxt[key];
         }
         ++p->ends;
     }

     int solve(string word) {
         int ret = ;
         int mask = ( << );

         Trie* p = this;
         for(int i = ; i < word.size(); ++i) {
             int key = word[i] - '';

             if(p->nxt[!key] != NULL) {
                 ret |= mask;
                 key = !key;
             }
             mask >>= ;
             p = p->nxt[key];
         }
         return ret;
     }
 };

 class Solution {
 public:
     int findMaximumXOR(vector<int>& nums) {
         Trie trie = Trie();
         vector< string > bits;
         int ans = -;
         int N = nums.size();

         for(int i = ; i < N; ++i) {
             bits.push_back(bitset<  >(nums[i]).to_string());
             trie.insert(bits[i]);
         }

         for(int i = ; i < N; ++i) {
             ans = max(ans, trie.solve(bits[i]));
         }

         return ans;
     }
 };