B题求调，只能通过42%

#include<bits/stdc++.h>
#define int long long
using namespace std;
int a[500010];
int per[500010];
signed main()
{
    std::ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n,m,k;
    cin>>n>>m>>k;
    int i;
    map<int,int>d;
    int cnt=0;
    for(i=1;i<=n;i++)
    {
        int x;
        cin>>x;
        if(d[x]==1)continue;
        d[x]=1;
        a[++cnt]=x;
    }
    sort(a+1,a+1+cnt);
    map<int,int>id;
    for(i=1;i<=cnt;i++)
    {
        if(a[i]-a[i-1]>1)
        per[i]=per[i-1]+a[i]-a[i-1]-1;
        else
        per[i]=per[i-1];
        if(id[per[i]]==0)
        id[per[i]]=i;
    }
    int maxn=0;
    for(i=1;i<=cnt;i++)
    {
        if(id[per[i]-k]==0)
        {
            maxn=max(maxn,i-id[per[i]]+1+k);
        }
        else
        maxn=max(maxn,i-id[per[i]-k]+1+k);
    }
    if(per[cnt]<k)
    {
        int d=k-per[cnt];
        cout<<min(n+k,min(m,n+d));
    }
    else
    cout<<maxn;
    return 0;
}