bzoj 2038: [2009国家集训队]小Z的袜子(hose)

Posted 2021-01-05 jaydenouyang

题目链接

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 inline int read()
 5 {
 6     int x=0,f=1;char ch=getchar();
 7     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
 8     while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
 9     return x*f;
10 }
11 
12 /********************************************************************/
13 
14 const int maxn = 50000+5;
15 int n, m;
16 int a[maxn];
17 int sz, belong[maxn];
18 ll ans, num[maxn];
19 ll up[maxn], dw[maxn];     //分子， 分母
20 
21 struct node{
22     int l, r;
23     int id;
24 }q[maxn];
25 
26 ll gcd(ll x, ll y){
27     if(y == 0) return x;
28     else gcd(y, x%y);
29 }
30 
31 bool cmp(node x, node y){
32     if(belong[x.l] == belong[y.l])
33         return x.r < y.r;
34     else
35         return belong[x.l] < belong[y.l];
36 }
37 
38 void update(int x, int d){
39     ans -= num[a[x]]*num[a[x]];
40     num[a[x]] += d;
41     ans += num[a[x]]*num[a[x]];
42 }
43 
44 int main(){
45     n = read(); m =read();
46     sz = ceil(sqrt(n*1.0));
47     for(int i =  1;i <= n;i++){
48         a[i] = read();
49         belong[i] = (i-1)/sz;
50     }
51     for(int i = 1;i <= m;i++){
52         q[i].l = read(); q[i].r = read();
53         q[i].id = i;
54     }
55     sort(q+1, q+1+m, cmp);
56     int pl = 1, pr = 0;
57     ans = 0;
58     for(int i = 1;i <= m;i++){
59         int id = q[i].id;
60         if(q[i].l == q[i].r){
61             up[id] = 0; dw[id] = 1;
62             continue;
63         }
64         if(pr < q[i].r){
65             for(int j = pr + 1;j <= q[i].r;j++){
66                 update(j, 1);
67             }
68         }
69         else{
70             for(int j = pr;j > q[i].r;j--){
71                 update(j, -1);
72             }
73         }
74         pr = q[i].r;
75         if(pl < q[i].l){
76             for(int j = pl;j < q[i].l;j++){
77                 update(j, -1);
78             }
79         }
80         else {
81             for(int j = pl - 1;j >= q[i].l;j--){
82                 update(j, 1);
83             }
84         }
85         pl = q[i].l;
86         ll aa = ans - q[i].r + q[i].l - 1;
87         ll bb = 1ll*(q[i].r - q[i].l + 1)*(q[i].r - q[i].l);
88         ll cc = gcd(aa, bb);
89         up[id] = aa/cc; dw[id] = bb/cc;
90     }
91     for(int i = 1;i <= m;i++){
92         printf("%lld/%lld
", up[i], dw[i]);
93     }
94     return 0;
95 }