【BZOJ2038】[2009国家集训队]小Z的袜子(hose)【莫队】

裸的模板。

/* Footprints In The Blood Soaked Snow */#include <cstdio>#include <algorithm>using namespace std;typedef long long LL;const int maxn = 50005, maxm = maxn, maxsqrtn = 224;int n, m, num[maxn], cnt[maxn];LL ans[maxm], deno[maxm];struct _query {int id, l, r;} q[maxm];inline int iread() {int f = 1, x = 0; char ch = getchar();for(; ch < '0' || ch > '9'; ch = getchar()) f = ch == '-' ? -1 : 1;for(; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';return f * x;}inline bool cmp(_query a, _query b) {return a.l / maxsqrtn < b.l / maxsqrtn || (a.l / maxsqrtn == b.l / maxsqrtn && a.r < b.r);}inline LL gcd(LL a, LL b) {for(; b; b ^= a ^= b ^= a %= b);return a;}int main() {n = iread(); m = iread();for(int i = 1; i <= n; i++) num[i] = iread();for(int i = 1; i <= m; i++) {int l = iread(), r = iread();q[i] = (_query){i, l, r};deno[i] = (LL)(q[i].r - q[i].l + 1) * (q[i].r - q[i].l);}sort(q + 1, q + 1 + m, cmp);LL tmp = 0;int l = 1, r = 0;for(int i = 1; i <= m; i++) {while(q[i].l < l) {l--;tmp += cnt[num[l]] << 1LL;cnt[num[l]]++;}while(l < q[i].l) {cnt[num[l]]--;tmp -= cnt[num[l]] << 1LL;l++;}while(q[i].r < r) {cnt[num[r]]--;tmp -= cnt[num[r]] << 1LL;r--;}while(r < q[i].r) {r++;tmp += cnt[num[r]] << 1LL;cnt[num[r]]++;}ans[q[i].id] = tmp;}for(int i = 1; i <= m; i++) {LL div = gcd(ans[i], deno[i]);printf("%lld/%lld\n", ans[i] / div, deno[i] / div);}return 0;}