P2709 小B的询问 莫队入门

#include <bits/stdc++.h>
#define ll long long 
using namespace std;
const int maxn = 1000005;//O(n*sqrt(n))
struct N{int l,r,id;}q[maxn];
int ans[maxn],a[maxn],Ans,unit;
int Be[maxn],color[maxn];
int cmp(N c,N d){
	return Be[c.l]==Be[d.l]? c.r<d.r: c.l<d.l;
}
int cmp2(N c,N d){
	return c.id<d.id;
}
ll gcd(ll a,ll b){return b>0?gcd(b,a%b):a; }
void revise(int x,int d){
 color[x]+=d;
if(d>0)Ans+=(color[x])*(color[x])-(color[x]-1)*(color[x]-1); 
if(d<0)Ans+=(color[x])*(color[x])-(color[x]+1)*(color[x]+1); 
}
int main()
{
	int n,m,l,r,k;
	scanf("%d%d%d",&n,&m,&k); unit = sqrt(n);
	for(int i=1;i<=n;i++)scanf("%d",&a[i]),Be[i] = i/unit+1;
	for(int i=1;i<=m;i++){
		scanf("%d %d",&q[i].l,&q[i].r);q[i].id = i;
	}
	sort(q+1,q+m+1,cmp);
	l = 1,r = 0;
	for(int i=1;i<=m;i++){
		while(l<q[i].l)revise(a[l],-1),l++;
		while(l>q[i].l)revise(a[l-1],1),l--;
		while(r<q[i].r)revise(a[r+1],1),r++;
		while(r>q[i].r)revise(a[r],-1),r--;
		
		ans[q[i].id] = Ans; 
 	}
	sort(q+1,q+m+1,cmp2);
	for(int i=1;i<=m;i++){
		printf("%d\n",ans[i]);
	}
	
	return 0;
}