Trie树 hdu4825 Xor Sum

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题意：给你一些数字，再询问Q个问题，每个问题给一个数字，使这个数字和之前给出的数字的异或和最大。

构造字典树，高位在前，低位在后

然后顺着字典树根向深处递归查询

#include<cstdio>#include<cmath>#include<cstring>#include<queue>#include<vector>#include<map>#include<set>#include<string>#include<iostream>#include<functional>#include<algorithm>using namespace std;typedef long long LL;typedef pair<LL, int> PLI;const int MX = 2e5 + 5;const int INF = 0x3f3f3f3f;struct Node {    Node *Next[2];    Node() {        Next[0] = Next[1] = NULL;    }};void trie_add(Node*root, int S) {    Node *p = root;    for(int i = 31; i >= 0; i--) {        int id = ((S & (1 << i)) != 0);        if(p->Next[id] == NULL) {            p->Next[id] = new Node();        }        p = p->Next[id];    }}int trie_query(Node*root, int S) {    Node *p = root;    int ans = 0;    for(int i = 31; i >= 0; i--) {        int id = ((S & (1 << i)) != 0);        if(p->Next[id ^ 1] != NULL) {            ans |= (id ^ 1) << i;            p = p->Next[id ^ 1];        } else {            ans |= id << i;            p = p->Next[id];        }    }    return ans;}int main() {    //freopen("input.txt", "r", stdin);    int T, n, Q, t, ansk = 0;    scanf("%d", &T);    while(T--) {        scanf("%d%d", &n, &Q);        Node *root = new Node();        for(int i = 1; i <= n; i++) {            scanf("%d", &t);            trie_add(root, t);        }        printf("Case #%d:\n", ++ansk);        while(Q--) {            scanf("%d", &t);            printf("%d\n", trie_query(root, t));        }    }    return 0;}

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