lightoj 1269(trie)

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题意：给出长度为n的序列，问选出任意区间的所有数字的异或值，最大最小各是多少。
题解：字典树经典问题，把前i个串的异或值都插入到字典树里，然后如果要找最大值，就把所有前缀去贪心出最大值，每次找和自己不一样的节点走，如果要找最小值，也是把所有前缀拿去贪心出最小值，每次找和自己当前位一样的节点，找最后一个分叉点，但要刨除自己。

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int N = 50005 * 33;int Next[N][2], val[N], sz, n, a[N];void init() {    memset(Next[0], 0, sizeof(Next[0]));    val[0] = 0;    sz = 1;}void insert(int s) {    int u = 0;    for (int i = 30; i >= 0; i--) {        int k = (s >> i) & 1;        if (!Next[u][k]) {            memset(Next[sz], 0, sizeof(Next[0]));            val[sz] = 0;            Next[u][k] = sz++;        }        u = Next[u][k];        val[u]++;    }}int queryMax(int s) {    int u = 0, res = 0;    for (int i = 30; i >= 0; i--) {        int k = ((s >> i) & 1) ^ 1;        if (Next[u][k])            res |= (1 << i);            else k ^= 1;        u = Next[u][k];    }    return res;}int queryMin(int s) {    int u = 0, res = 0;    for (int i = 30; i >= 0; i--) {        int k = (s >> i) & 1;        if (Next[u][k ^ 1] && val[Next[u][k]] <= 1) {            k ^= 1;            res |= (1 << i);        }        u = Next[u][k];     }    return res;}int main() {    int t, cas = 1;    scanf("%d", &t);    while (t--) {        init();        scanf("%d", &n);        insert(0);        int x;        for (int i = 1; i <= n; i++) {            scanf("%d", &x);            a[i] = a[i - 1] ^ x;            insert(a[i]);        }        int resMax = -1, resMin = (1 << 31) - 1;        for (int i = 0; i <= n; i++) {            resMax = max(resMax, queryMax(a[i]));            resMin = min(resMin, queryMin(a[i]));        }        printf("Case %d: %d %d\n", cas++, resMax, resMin);    }    return 0;}

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