Codeforces Round #340 (Div. 2) E. XOR and Favorite Number

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莫队，贴一个关于莫队讲解的好文章。http://blog.csdn.net/bossup/article/details/39236275

#include <cstdio>#include <algorithm>#include <cmath>using namespace std;typedef long long ll;const int maxn = 100100;int n, m, k;int num[maxn], block[maxn];ll ans[maxn];int cnt[2000100];struct query{    int l, r, id;}node[maxn];int cmp(query A, query B){    if (block[A.l] == block[B.l]) return A.r < B.r;    else return A.l < B.l;}int main(){    scanf("%d%d%d", &n, &m, &k);    int block_size = sqrt(n);    num[0] = 0;    for (int i = 1; i <= n; i++)    {        scanf("%d", &num[i]);        num[i] ^= num[i - 1];        block[i] = i / block_size;    }    for (int i = 0; i < m; i++)    {        scanf("%d%d", &node[i].l, &node[i].r);        node[i].l--;        node[i].id = i;    }    sort(node, node + m, cmp);    int l = 1, r = 0;    ll tmp = 0;    for (int i = 0; i < m; i++)    {        while (r < node[i].r)        {            r++;            tmp += cnt[num[r] ^ k];            cnt[num[r]]++;        }        while (r > node[i].r)        {            cnt[num[r]]--;            tmp -= cnt[num[r] ^ k];            r--;        }        while (l < node[i].l)        {            cnt[num[l]]--;            tmp -= cnt[num[l] ^ k];            l++;        }        while(l > node[i].l)        {            l--;            tmp += cnt[num[l] ^ k];            cnt[num[l]]++;        }        ans[node[i].id] = tmp;    }    for (int i = 0; i < m; i++)        printf("%I64d\n", ans[i]);    return 0;}

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