【luogu 2709 / BZOJ 3781】小B的询问

【原题题面】传送门

【题解大意】

莫队。这题未免太果。

【code】

#include<bits/stdc++.h>
using namespace std;
#define File ""
#define ll long long
#define ull unsigned long long
inline void file(){
    freopen(File".in","r",stdin);
    freopen(File".out","w",stdout);
}
inline int read(){
    int x=0,f=1;   char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1; ch=getchar();}
    while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+ch-'0'; ch=getchar();}
    return x*f;
}
const int mxn = 5e4+5;
int n,m,k;
int Block;
int a[mxn],ans[mxn],cnt[mxn];
struct Q{
    int l,r,id;
}q[mxn];
inline bool cmp(Q x,Q y){
    if((x.l/Block) ^ (y.l/Block)) return x.l < y.l;
    else if((x.l/Block)&1) return x.r < y.r;
    else return x.r > y.r;
}
ll answer(0);
inline void mov(int x,int d){
    answer -= cnt[a[x]]*cnt[a[x]];
    cnt[a[x]] += d;
    answer += cnt[a[x]]*cnt[a[x]];
}
int main(){
//    file();
    n = read(),m = read(),k = read();
    Block = sqrt(n);
    for(int i = 1;i <= n; ++i) a[i] = read();
    for(int i = 1;i <= m; ++i) q[i].l = read(),q[i].r = read(),q[i].id = i;
    sort(q+1,q+1+m,cmp);
    int l(1),r(0);
    for(int i = 1;i <= m; ++i){
        int ql = q[i].l,qr = q[i].r;
        while(ql < l) mov(l-1,1),l--;
        while(ql > l) mov(l,-1),l++;
        while(qr < r) mov(r,-1),r--;
        while(qr > r) mov(r+1,1),r++;
        ans[q[i].id] = answer;
    }
    for(int i = 1;i <= m; ++i) printf("%d\n",ans[i]);
    return 0;
}
/*
6 4 3
1 3 2 1 1 3
1 4
2 6
3 5
5 6
*/