代码

//190ms 1704kb
#include <algorithm>

int query_kth(const int *A,int na,const int *B,int nb,const int *C,int n_c, int k)
{
    const int myINF=0x7fffffff;
    int nowa=-1,nowb=-1,nowc=-1,delta,a,b,c,mn;
    while(k>2)
    {
        delta=k/3;
        a=nowa+delta<=n_a?get_a(nowa+delta):myINF,
        b=nowb+delta<=n_b?get_b(nowb+delta):myINF,
        c=nowc+delta<=n_c?get_c(nowc+delta):myINF;
        mn=std::min(a,std::min(b,c));
        if(mn==a) nowa+=delta;
        else if(mn==b) nowb+=delta;
        else if(mn==c) nowc+=delta;
        k-=delta;
    }
    int A[7];
    A[1]=get_a(nowa+1), A[2]=get_a(nowa+2);
    A[3]=get_b(nowb+1), A[4]=get_b(nowb+2);
    A[5]=get_c(nowc+1), A[6]=get_c(nowc+2);
    std::sort(A+1,A+7);
    return A[k];
}

评测结果