Add files via upload

Author: assassint2017

Maximum XOR of Two Numbers in an Array/Maximum_XOR_of_Two_Numbers_in_an_Array.cpp

@@ -0,0 +1,95 @@
+// 很明显可以使用n2的时间复杂度以及常数的空间复杂度解决问题
+// 但是可以用前缀树来以空间换取时间实现线性的时间复杂度
+// https://leetcode.com/problems/maximum-xor-of-two-numbers-in-an-array/discuss/130427/()-92
+
+// Runtime: 164 ms, faster than 23.69% of C++ online submissions for Maximum XOR of Two Numbers in an Array.
+// Memory Usage: 108.1 MB, less than 10.00% of C++ online submissions for Maximum XOR of Two Numbers in an Array.
+
+struct TrieNode
+{
+    TrieNode* left = nullptr;
+    TrieNode* right = nullptr;
+};
+
+class Solution 
+{
+public:
+    Solution() : root(new TrieNode()) {}
+    
+    ~Solution() { clear(root); }
+    
+    int findMaximumXOR(vector<int>& nums) 
+    {
+        // 建立前缀树
+        buildTrie(nums);
+        
+        // 迭代查找
+        int res = INT_MIN;
+        for (auto item : nums)
+        {
+            int temp = 0;
+            TrieNode* head = root;
+            for (int i = 1, ptr = 0x40000000; i < 32; ++i, ptr >>= 1)
+            {
+                int carry = 0;
+
+                if (ptr & item)
+                {
+                    if (head->left == nullptr) head = head->right;
+                    else ++carry, head = head->left;
+                }
+                else
+                {
+                    if (head->right == nullptr) head = head->left;
+                    else ++carry, head = head->right;
+                }
+                
+                temp *= 2;
+                temp += carry;
+            }
+            res = temp > res ? temp : res;
+        }
+        return res;
+    }
+
+private:
+    TrieNode* root = nullptr;
+
+private:
+    void buildTrie(const vector<int>& nums)
+    {
+        for (auto num : nums)
+        {
+            TrieNode* head = root;
+            for (int i = 1, ptr = 0x40000000; i < 32; ++i, ptr >>= 1)
+            {
+                if (ptr & num)
+                {
+                    if (head->right == nullptr)
+                    {
+                        TrieNode* node = new TrieNode();
+                        head->right = node;
+                    }
+                    head = head->right;
+                }
+                else
+                {
+                    if (head->left == nullptr)
+                    {
+                        TrieNode* node = new TrieNode();
+                        head->left = node;
+                    }
+                    head = head->left;
+                }
+            }
+        }
+    }
+    
+    void clear(TrieNode* root)
+    {
+        if (root == nullptr) return ;
+        clear(root->left);
+        clear(root->right);
+        delete root;
+    }
+};