SPOJ DQUERY 区间内不同数的个数

题目：给你n个数，m个询问，问区间[L,R]内的不同数的个数

代码：

#pragma comment(linker, "/STACK:1024000000,1024000000")#include<iostream>#include<algorithm>#include<cstdio>#include<cmath>#include<cstring>#include<string>#include<vector>#include<map>#include<set>#include<queue>#include<stack>#include<list>#include<numeric>using namespace std;#define PI acos(-1.0)#define LL long long#define ULL unsigned long long#define INF 0x3f3f3f3f#define mm(a,b) memset(a,b,sizeof(a))#define PP puts("*********************");template<class T> T f_abs(T a){ return a > 0 ? a : -a; }template<class T> T gcd(T a, T b){ return b ? gcd(b, a%b) : a; }template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;}// 0x3f3f3f3f3f3f3f3f// 0x3f3f3f3fconst int maxn=1e5+50;const int maxm=maxn*30;int arr[maxn];//原数组int root[maxn],lson[maxm],rson[maxm],cnt[maxm];//根节点，左儿子，右儿子，区间内的数出现次数的前缀和int tot,n;void init(){    tot=1;    root[0]=lson[0]=rson[0]=cnt[0]=0;//建一棵空树}int update(int rt,int pos,int val){    int newrt=tot++,temp=newrt;    cnt[newrt]=cnt[rt]+val;    int l=1,r=n;    while(l<r){        int mid=(l+r)/2;        if(pos<=mid){            r=mid;            lson[newrt]=tot++;rson[newrt]=rson[rt];            newrt=lson[newrt];rt=lson[rt];        }        else{            l=mid+1;            lson[newrt]=lson[rt];rson[newrt]=tot++;            newrt=rson[newrt];rt=rson[rt];        }        cnt[newrt]=cnt[rt]+val;    }    return temp;}int query(int rt,int pos){    int l=1,r=n;    int res=0;    while(l<r){        int mid=(l+r)/2;        if(pos<=mid){            r=mid;            res+=cnt[rson[rt]];            rt=lson[rt];        }        else{            l=mid+1;            rt=rson[rt];        }    }    res+=cnt[rt];    return res;}map<int,int> mp;int main(){    int m,L,R;    while(~scanf("%d",&n)){        for(int i=1;i<=n;i++)            scanf("%d",&arr[i]);        init();        mp.clear();        for(int i=1;i<=n;i++){            if(mp.count(arr[i])){                root[i]=update(root[i-1],mp[arr[i]],-1);                root[i]=update(root[i],i,1);            }            else                root[i]=update(root[i-1],i,1);            mp[arr[i]]=i;        }        scanf("%d",&m);        while(m--){            scanf("%d%d",&L,&R);            int ans=query(root[R],L);            printf("%d\n",ans);        }    }    return 0;}