数组中两个数的最大异或值（字典树||前缀树）

Posted 2021-06-06 秦枫-_-

以下分别用了C++和java实现了两种构建前缀树的版本 可以先看C++容易理解

C++版本

#include <iostream>
#include <vector>
using namespace std;
struct Tree
{
    Tree* left = NULL;
    Tree* right = NULL;
};
class Solution {
    Tree* root = new Tree();
    void construct(int x) {
        Tree* child = root;
        for (int i = 30; i >= 0; i--) {
            int t = (x >> i) & 1;
            if (t == 0) {
                if (child->left == NULL)
                    child->left = new Tree();
                child = child->left;
            }
            else {
                if (child->right == NULL)
                    child->right = new Tree();
                child = child->right;
            }
        }
    }
    int search(int x) {
        Tree* child = root;
        int res = 0;
        for (int i = 30; i >= 0; i--) {
            int t = (x >> i) & 1;
            if (t == 1) {
                if (child->left == NULL)
                    child = child->right;
                else
                {
                    res += (1 << i);
                    child = child->left;
                }
            }
            else {
                if (child->right == NULL)
                    child = child->left;
                else
                {
                    res += (1 << i);
                    child = child->right;
                }
            }
        }
        return res;
    }
public:
    int findMaximumXOR(vector<int> nums) {
        int res = 0;
        for (int i = 0; i < nums.size(); i++) {
            construct(nums[i]);
        }
        for (int i = 0; i < nums.size(); i++) {
            res = max(res, search(nums[i]));
        }
        return res;
    }
};

Java版本

class Solution {
    class Tree{
        Tree []son=new Tree[2];
    }
    Tree root=new Tree();
    void construct(int x){
        Tree child=root;
        for(int i=30;i>=0;i--){
            int t=(x>>i)&1;
            if(child.son[t]==null)
            child.son[t]=new Tree();
            child=child.son[t];
        }
    }
    int search(int x){
        Tree child=root;
        int res=0;
        for(int i=30;i>=0;i--){
            int t=(x>>i)&1;
            if(child.son[t^1]==null){
                child=child.son[t];
            }else{
                 res+=(1<<i);
                 child=child.son[t^1];
            }
        }
        return res;
    }
    public int findMaximumXOR(int[] nums) {
       int res=0;
       for(int i=0;i<nums.length;i++){
           construct(nums[i]);
       }
       for(int i=0;i<nums.length;i++){
           res=Math.max(res,search(nums[i]));
       }
       return res;
    }
}