代码

#include <algorithm> 
#include <cstring>

using namespace std;

int query_kth(const int *a, int n_a, const int *b, int n_b, const int *c, int n_c, int k)
{
    static const int *num[] = {a, b, c}, n[] = {n_a, n_b, n_c}, N = 3, INF = 1 << 30;
    static int i, j, m[N], s[N], x, y;
    for (memset(m, x = 0, sizeof(m)); k -= x; m[j] += x)
    {
        x = (k - N + 1) / N;
        for (i = j = 0; i < 3; ++i)
        {
            if ((y = m[i] + x) < n[i])
                s[i] = num[i][y];
            else
                s[i] = INF;
            if (s[j] > s[i])
                j = i;
        }
        ++x;
    }
    return s[j];
}

评测结果