Leetcode median of two sorted arrays problem

median_of_two_sorted_arrays.cpp

#include <iostream>
#include <vector>

using namespace std;

double findMedianSortedArrays(vector<int>& nums1, vector<int>& nums2) {
    int size1 = nums1.size();
    int size2 = nums2.size();
    if (size1 < size2)  //if one array is smaller then we want smaller in nums2 
        return findMedianSortedArrays(nums2, nums1);

    if (size2 == 0)   //single list
        return (double(nums1[(size1-1)/2])+nums1[size1/2])/2;

    int start1 = 0, start2 = 0;
    int len1 = size1, len2 = size2;
    bool beyond_start1=false, beyond_start2=false, beyond_end1=false, beyond_end2=false;
    while (true) { 
        int L1 = (beyond_start1) ? INT_MIN : nums1[start1 + ((len1-1)/2)];
        int L2 = (beyond_start2) ? INT_MIN : nums2[start2 + ((len2-1)/2)];
        int R1 = (beyond_end1) ? INT_MAX : nums1[start1 + (len1/2)];
        int R2 = (beyond_end2) ? INT_MAX : nums2[start2 + (len2/2)];

        if (L1 > R2) {  //partition list 2 window to use 2nd half (right half)
            if (len2==1) {  //beyond end of list 2 edge case
                if (start2<size2-1)
                    len2++;
                else
                    beyond_end2 = true;
                if (len1==1) { //and beyond start of list1 edge case
                    if (start1>0) {
                        len1++;
                        start1--;
                    }
                    else
                        beyond_start1 = true;
                }
                else
                    len1--;
            }
            else {
                int new_len2 = (len2/2);
                start2 += ((len2+1)/2);
                int num_discarded = len2 - new_len2;
                len2 = new_len2;
                //also discard num_discarded from right side of list 1 window
                len1 = len1 - num_discarded; 
            }
        }
        else if (R1 < L2) { //partition list 2 window to use 1st half (left half)
            if (len2==1) {  //before start of list 2 edge case
                if (start2>0) {
                    start2--;
                    len2++;
                }
                else
                    beyond_start2 = true;
                if (len1==1) { //beyond end of list 1 edge case
                    if (start1<size1-1)
                        len1++;
                    else
                        beyond_end1 = true;
                }
                else {
                    start1++;
                    len1--;
                }
            }
            else {
                int new_len2 = (len2/2);
                int num_discarded = len2 - new_len2;
                len2 = new_len2;
                //also discard num_discarded from left side of list1 window
                start1 += num_discarded;
                len1 -= num_discarded;
            }
        }
        else {
            return ((double(max(L1,L2))+min(R1,R2))/2);
        }
    }
    
    return -1;
}

int main() {
    cout << "findMedianSortedArrays({3,6,8,11,15,18},{1,2,4,7}) = ";
    vector<int> nums1 = {3,6,8,11,15,18};
    vector<int> nums2 = {1,2,4,7};
    cout << findMedianSortedArrays(nums1, nums2) << endl;

    return 0;
}