Codeforces Round #398 (Div. 2) D. Cartons of milk

#include<bits/stdc++.h>

using namespace std;

#define X first
#define Y second
#define eps  1e-2
#define gcd __gcd
#define pb push_back
#define PI acos(-1.0)
#define lowbit(x) (x)&(-x)
#define bug printf("!!!!!\n");
#define mem(x,y) memset(x,y,sizeof(x))

typedef long long LL;
typedef long double LD;
typedef pair<int,int> pii;
typedef unsigned long long uLL;

const int maxn = 1e6+2;
const int INF  = 1<<30;
const int mod  = 1e9+7;

int n,m,k,f[maxn],s[maxn];
pair<int,int> p[2][maxn];

bool cmp(pair<int,int> a,pair<int,int> b){
    if(a.first==b.first) return a.second>b.second;
    return a.first>b.first;
}

bool check(int x){
    int i=n,j=x,now=1;
    while(i||j){
        int day=(now-1)/k;
        // cout<<day<<endl;
        if(i==0){
            if(p[1][j].first<day) return 0;
            --j;
        }else if(j==0){
            if(p[0][i].first<day) return 0;
            --i;
        }else{
            if(p[0][i].first<=p[1][j].first){
                if(p[0][i].first<day) return 0;
                --i;
            }else{
                if(p[1][j].first<day) return 0;
                --j;
            }
        }
        ++now;
        // cout<<i<<" "<<j<<endl;
    }
    if(i) return 0;
    else return 1;
}

void solve(){
    scanf("%d%d%d",&n,&m,&k);
    for(int i=1;i<=n;i++) scanf("%d",&f[i]),p[0][i]={f[i],i};
    for(int i=1;i<=m;i++){scanf("%d",&s[i]);p[1][i]={s[i],i};}
    sort(p[0]+1,p[0]+1+n,cmp);
    sort(p[1]+1,p[1]+1+m,cmp);
    // check(3);
    // return ;
    int l=0,r=m;
    while(l<r){
        int mid=(l+r+1)>>1;
        if(check(mid)) l=mid;
        else r=mid-1;
    }
    if(check(l)==0){
        cout<<-1<<endl;
        return ;
    }
    cout<<l<<endl;
    for(int i=l;i>=1;i--){
        cout<<p[1][i].second<<" ";
    }cout<<endl;
    return;
}

int main()
{
//    freopen("in.txt","r",stdin);
//    freopen("out.txt","w",stdout);
//    ios::sync_with_stdio(false);
    int t = 1;
    //scanf("%d",&t);
    while(t--){
    //    printf("Case %d: ",cas++);
        solve();
    }
    return 0;
}