[luogu2709] 小B的询问

Posted 2021-01-24 neworld2002

传送门

直接莫队即可。

#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#define MAXN 50005

struct Node {
    int l,r,num,ans;
}G[MAXN];

int book[MAXN];
int cur[MAXN],rec[MAXN];

int N,M,K,size;
int ans = 0;

inline void work(int x,int u) {
    ans -= book[cur[x]]*book[cur[x]];
    book[cur[x]] += u;
    ans += book[cur[x]]*book[cur[x]];
}

inline bool cmp(Node a,Node b) {
    return (a.l/size)^(b.l/size) ? a.l<b.l : ((a.l/size)&1 ? a.r<b.r : a.r>b.r);
}

int main() {
    
    scanf("%d%d%d",&N,&M,&K);
    for(int i=1;i<=N;++i) {
        scanf("%d",&cur[i]);
    }
    size = floor(sqrt(N));
    std::memset(book,0,sizeof(book));
    
    for(int i=1;i<=M;++i) {
        scanf("%d%d",&G[i].l,&G[i].r);
        G[i].num = i;
    }
    
    std::sort(G+1,G+1+M,cmp);
    int L = G[1].l,R = G[1].r;
    ans = 0;
    for(int i=L;i<=R;++i) work(i,1);
    
    for(int i=1;i<=M;++i) {
        while(L>G[i].l) work(--L,1);
        while(R>G[i].r) work(R--,-1);
        while(R<G[i].r) work(++R,1);
        while(L<G[i].l) work(L++,-1);
        G[i].ans = ans; rec[G[i].num] = i;
    }
    for(int i=1;i<=M;++i) printf("%d
",G[rec[i]].ans);
    return 0;   
}