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

Posted 2020-09-16 Flowersea

链接：

http://codeforces.com/contest/617/problem/E

代码：

31 struct node {
32     int l, r, id;
33 }q[MAXN];
34 
35 int n, m, k;
36 int a[MAXN];
37 int pos[MAXN];
38 ll ans[MAXN];
39 ll sum[2000007];
40 
41 bool cmp(node a, node b) {
42     if (pos[a.l] == pos[b.l]) return a.r < b.r;
43     return pos[a.l] < pos[b.l];
44 }
45 
46 int L = 1, R = 0;
47 ll Ans = 0;
48 
49 void add(int x) {
50     Ans += sum[a[x] ^ k];
51     sum[a[x]]++;
52 }
53 
54 void del(int x) {
55     sum[a[x]]--;
56     Ans -= sum[a[x] ^ k];
57 }
58 
59 int main() {
60     ios::sync_with_stdio(false), cin.tie(0);
61     cin >> n >> m >> k;
62     int sz = sqrt(n);
63     rep(i, 1, n + 1) {
64         cin >> a[i];
65         a[i] ^= a[i - 1];
66         pos[i] = i / sz;
67     }
68     rep(i, 0, m) {
69         cin >> q[i].l >> q[i].r;
70         q[i].id = i;
71     }
72     sort(q, q + m, cmp);
73     sum[0] = 1;
74     rep(i, 0, m) {
75         while (L < q[i].l) del(L - 1), L++;
76         while (L > q[i].l) L--, add(L - 1);
77         while (R < q[i].r) R++, add(R);
78         while (R > q[i].r) del(R), R--;
79         ans[q[i].id] = Ans;
80     }
81     rep(i, 0, m) cout << ans[i] << endl;
82     return 0;
83 }