小Z的袜子(hose)
莫队经典
1 #include <iostream> 2 #include <cmath> 3 #include <cstdio> 4 #include <cstring> 5 #include <algorithm> 6 #define LL long long 7 using namespace std; 8 const int maxn = 50010; 9 LL gcd(LL a, LL b){ 10 return b == 0 ? a : gcd(b, a % b); 11 } 12 struct Qry{ 13 LL l, r, pos, id; 14 LL a, b; 15 bool operator < (const Qry &a)const{ 16 if(pos == a.pos) return r < a.r; 17 return l < a.l; 18 } 19 }q[maxn]; 20 LL c[maxn], s[maxn]; 21 LL ans; 22 void update(LL p, LL v){ 23 ans += 2 * v * s[c[p]] + 1; 24 s[c[p]] += v; 25 } 26 bool cmp(Qry x, Qry y){ 27 return x.id < y.id; 28 } 29 void solve(LL n, LL m){ 30 LL l = 1, r = 0; 31 ans = 0; 32 for(LL i = 0; i < m; i++){ 33 while(l < q[i].l) update(l++, -1); 34 while(l > q[i].l) update(--l, 1); 35 while(r > q[i].r) update(r--, -1); 36 while(r < q[i].r) update(++r, 1); 37 if(q[i].l == q[i].r) {q[i].a = 0; q[i].b = 1; continue;} 38 q[i].a = ans - (q[i]. r - q[i]. l + 1); 39 q[i].b = (q[i]. r - q[i]. l + 1) * (q[i].r - q[i].l); 40 LL g = gcd(q[i].a, q[i].b); 41 q[i].a /= g; q[i].b /= g; 42 } 43 sort(q, q + m, cmp); 44 } 45 46 int main(){ 47 LL n, m; 48 while(scanf("%lld %lld", &n, &m) != EOF){ 49 memset(s, 0, sizeof s); 50 for(LL i = 1; i <= n; i++){ 51 scanf("%lld", &c[i]); 52 } 53 LL SZ = sqrt(n * 1.0); 54 for(LL i = 0; i < m; i++){ 55 scanf("%lld %lld", &q[i].l, &q[i].r); 56 q[i].id = i; 57 q[i].pos = (q[i].l - 1) / SZ + 1; 58 } 59 sort(q, q + m); 60 solve(n, m); 61 for(LL i = 0; i < m; i++) printf("%lld/%lld ", q[i].a, q[i].b); 62 } 63 }