ACdream 1427—— Nice Sequence——————【线段树单点更新，区间查询】

Problem Description

Let us consider the sequence a1, a2,..., an of non-negative integer numbers. Denote as ci,j the number of occurrences of the number i among a1,a2,..., aj. We call the sequence k-nice if for all i1<i2 and for all j the following condition is satisfied: ci1,j ≥ ci2,j −k.

Given the sequence a1,a2,..., an and the number k, find its longest prefix that is k-nice.

Input

The first line of the input file contains n and k (1 ≤ n ≤ 200 000, 0 ≤ k ≤ 200 000). The second line contains n integer numbers ranging from 0 to n.

Output

Output the greatest l such that the sequence a1, a2,..., al is k-nice.

Sample Input

10 1
0 1 1 0 2 2 1 2 2 3
2 0
1 0

Sample Output

8
0


题目大意：给出n，k。n表示长度为n的序列，且序列中的值都是0---n的。定义ci,j表示数字i在a1，a2...aj中出现的次数，定义k-nice序列，即i1<i2且满足不等式ci1,j ≥ ci2,j −k。

解题思路：我们将序列映射到线段树的叶子上。那么对于ai来说，我们单点更新数字ai出现的次数，然后从1---ai中查询某数字出现最少的次数，如果不满足的不等式，那么就直接结束了。其实只需要用线段树维护每个数字出现的次数即可。

#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<iostream>
using namespace std;
#define mid (L+R)/2
#define lson rt*2,L,mid
#define rson rt*2+1,mid+1,R
const int INF=0x3f3f3f3f;
const int maxn=3*(1e5);
struct SegTree{
    int v;
}segtrees[maxn*4];
int a[maxn],times[maxn];
void build(int rt,int L,int R){
    if(L==R){
        segtrees[rt].v=0;
        return ;
    }
    build(lson);
    build(rson);
}
void PushUp(int rt){
    segtrees[rt].v=min(segtrees[rt*2].v,segtrees[rt*2+1].v);
}
void update(int rt,int L,int R,int key){
    if(L==R){
        segtrees[rt].v++;
        return ;
    }
    if(key<=mid)
        update(lson,key);
    else
        update(rson,key);
    PushUp(rt);
}
int query(int rt,int L,int R,int l_ran,int r_ran){
    if(l_ran<=L&&R<=r_ran){
        return segtrees[rt].v;
    }
    int ret=INF;
    if(l_ran<=mid){
        ret =min(ret,query(lson,l_ran,r_ran));
    }
    if(r_ran>mid){
        ret = min(ret,query(rson,l_ran,r_ran));
    }
    return ret;
}
int main(){
    int n,k;
    while(scanf("%d%d",&n,&k)!=EOF){
        memset(times,0,sizeof(times));
        build(1,0,n);
        int flag=0;
        int ans=n;
        for(int i=1;i<=n;i++){
            scanf("%d",&a[i]);
            if(flag) continue;
            times[a[i]]++;
            update(1,0,n,a[i]);
            int xx=query(1,0,n,0,a[i]);
            if(xx<times[a[i]]-k){
                ans=i-1;
                flag=1;
            }
        }
        printf("%d
",ans);
    }
    return 0;
}