UVA 11235 Frequent values

 离散化+RMQ。

离散化存储每个数出现的次数，再RMQ查询max次数。

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;

const int maxn=100005;

int count[maxn];
int num[maxn],ll[maxn],rr[maxn];
int tot;
int d[maxn][50];

int rmq (int l,int r){
    int k=0;
    while ( (1<<(k+1)) <= r-l+1 ) k++;
    return max(d[l][k],d[r-(1<<k)+1][k]);
}

int main (){
    int n,q;
    while (cin>>n&&n){
        cin>>q;
        tot=0;
        memset (count,0,sizeof count);
        int temp=99999999;
        ll[tot]=0;
        for (int i=1;i<=n;i++){
            int x;
            cin>>x;
            if (x!=temp){
                temp=x;
                rr[tot]=i-1;
                tot++;
                ll[tot]=i;
            }
            count[tot]++;
            num[i]=tot;
        }
        rr[tot]=n;
        for (int i=1;i<=tot;i++) d[i][0]=count[i];//cout<<count[i]<<" ";cout<<endl;
        for (int j=1;(1<<j)<=tot;j++){
            for (int i=1;i+(1<<(j-1))<=tot;i++){
                d[i][j]=max (d[i][j-1],d[i+(1<<(j-1))][j-1]);
            }
        }
        while (q--){
            int l,r;
            cin>>l>>r;
            int ans=0;
            if (num[l]==num[r]){
                cout<<r-l+1<<endl;
                continue ;
            }
            //if (rr[num[l]]<=r)
                ans=max (ans,rr[num[l]]-l+1);
            //if (ll[num[r]]>=l)
                ans=max (ans,r-ll[num[r]]+1);//cout<<num[l]+1<<" "<<num[r]-1<<"err"<<endl;
            if (num[l]+1<=num[r]-1)
                ans=max (ans,rmq (num[l]+1,num[r]-1));//cout<<rmq (num[l]+1,num[r]-1)<<"aaa"<<endl;
            cout<<ans<<endl;
        }
    }
    return 0;
}