Leetcode Maximum XOR of Two Numbers in an Array

class Solution {
public:
int findMaximumXOR(vector<int>& nums) {
int mask = 0;
int re = 0;
for(int i = 31; i >=0; -- i) {
mask |= (1 << i);
map<int, bool> prefix;
for(int j = 0; j < nums.size(); ++ j) {
prefix[mask & nums[j]] = true;
}

int temp = re;
temp |= (1 << i);
for(int j = 0; j < nums.size(); ++ j) {
if(prefix[temp ^ (nums[j] & mask)]) re = temp;
}
}

return re;
}
};

class Solution {
public:
int findMaximumXOR(vector<int>& nums) {
TrieTree* root = buildTrieTree(nums);
//root = root->buildTrieTree(nums);
int re = 0;
for(int i = 0; i < nums.size(); ++ i) {
re = max(re, findIt(root, nums[i]));
}

return re;
}

private:
class TrieTree {
public:
TrieTree* c[2];
TrieTree() {
c[0] = NULL, c[1] = NULL;
};
};
TrieTree* buildTrieTree(vector<int> nums) {
TrieTree* root = new TrieTree(), *next = NULL;
for(int i = 0; i < nums.size(); ++ i) {
int num = nums[i]; //cout << num << endl;
next = root;

for(int j = 31; j >=0; --j) {
bool bit = (num >> j) & 1; //cout <<num << ((num >>= j) & 1) << endl;
if(next->c[bit]) {
next = next->c[bit];
}
else {
TrieTree* child = new TrieTree();
next->c[bit] = child;
next = child;
}
}
}

return root;
}

int findIt(TrieTree* root, int num) {
int re = 0;
int rnum = ~num;

for(int i = 31; i >=0; -- i) {
bool bit =(rnum >> i) & 1;
if(root->c[bit]) {
re |= (1 << i);
root = root->c[bit];
}
else {
root = root->c[!bit];

4000
}
}

return re;
}
};