find Kth number in two sorted arrays.

findKthSmallest.cpp

int findKthSmallest(int vec1[], int n1, int vec2[], int n2, int k)
{
    if (n1 == 0)
        return vec2[k - 1];
    else if (n2 == 0)
        return vec1[k - 1];
    if (k == 1)
        return vec1[0] < vec2[0] ? vec1[0] : vec2[0];

    int idx1 = n1 * 1.0 / (n1 + n2) * (k - 1);
    int idx2 = k - idx1 - 2;

    if (vec1[idx1] == vec2[idx2])
        return vec1[idx1];
    else if (vec1[idx1] < vec2[idx2])
        return findKthSmallest(&vec1[idx1 + 1], n1 - idx1 - 1, vec2, idx2+1, k - idx1 - 1);
    else
        return findKthSmallest(vec1, idx1+1, &vec2[idx2 + 1], n2 - idx2 - 1, k - idx2 - 1);
}

References:

• https://www.cnblogs.com/TenosDoIt/p/3554479.html