SPOJ

SPOJ - 3267

主席树的又一种写法。 从后端点开始添加主席树， 然后如果遇到出现过的元素先把那个点删除， 再更新树， 最后查询区间就好了。

#include<bits/stdc++.h>
using namespace std;
#define Fopen freopen("_in.txt","r",stdin); freopen("_out.txt","w",stdout);
#define LL long long
#define ULL unsigned LL
#define fi first
#define se second
#define pb push_back
//#define lson l,m,rt<<1
//#define rson m+1,r,rt<<1|1
#define max3(a,b,c) max(a,max(b,c))
#define min3(a,b,c) min(a,min(b,c))
typedef pair<int,int> pll;
const int INF = 0x3f3f3f3f;
const LL mod =  (int)1e9+7;
const int N = 3e4 + 100;
const int M = 1e6 + 100;
int root[N], lson[M], rson[M], cnt[M];
int a[N];
map<int,int> mp;
int tot;
int Build(int l, int r){
    int now = ++tot;
    cnt[now] = 0;
    if(l < r){
        int m = l+r >> 1;
        lson[now] = Build(l, m);
        rson[now] = Build(m+1, r);
    }
    return now;
}
int Update(int l, int r, int pre, int c, int v){
    int now = ++tot;
    cnt[now] = cnt[pre] + v;
    if(l < r){
        int m = l+r >> 1;
        if(c <= m){
            rson[now] = rson[pre];
            lson[now] = Update(l, m, lson[pre], c, v);
        }
        else {
            lson[now] = lson[pre];
            rson[now] = Update(m+1, r, rson[pre], c, v);
        }
    }
    return now;
}
int Query(int l, int r, int p, int R){
    if(l == r) return cnt[p];
    int m = l+r >> 1;
    if(R <= m){
        return Query(l, m, lson[p], R);
    }
    else {
        return Query(m+1,r,rson[p],R) + cnt[lson[p]];
    }
}
int main(){
    int n;
    scanf("%d", &n);
    for(int i = 1; i <= n; i++) scanf("%d", &a[i]);
    root[n+1] = Build(1, n);
    for(int i = n; i >= 1; i--){
        if(mp[a[i]] == 0){
            root[i] = Update(1, n, root[i+1], i, 1);
        }
        else {
            int tmp = Update(1, n, root[i+1], mp[a[i]], -1);
            root[i] = Update(1, n, tmp, i, 1);
        }
        mp[a[i]] = i;
    }
    int m, l, r;
    scanf("%d", &m);
    for(int i = 1; i <= m; i++){
        scanf("%d%d", &l, &r);
        printf("%d
", Query(1,n,root[l],r));
    }
    return 0;
    
}