4-median-of-two-sorted-arrays.h

class Solution {
public:
	double findMedianSortedArrays(vector<int>& nums1, vector<int>& nums2) {
        int len1 = nums1.size();
	    int len2 = nums2.size();
        int len = len1 + len2;
        if(len & 1)
            return findKth(nums1, 0, nums2, 0, len / 2 + 1);
        else
            return (findKth(nums1, 0, nums2, 0, len / 2) + findKth(nums1, 0, nums2, 0, len / 2 + 1)) / 2;
	}
    
	// find kth number of two sorted array
	double findKth(vector<int>& nums1, int i1, vector<int>& nums2, int i2, int k) {
		if (i1 >= nums1.size()) {
			return nums2[i2 + k - 1];
		}
		if (i2 >= nums2.size()) {
			return nums1[i1 + k - 1];
		}
		if (k == 1) {
			return min(nums1[i1], nums2[i2]);
		}
		int key1 = i1 + k / 2 - 1 >= nums1.size() ? INT_MAX : nums1[i1 + k / 2 - 1];
		int key2 = i2 + k / 2 - 1 >= nums2.size() ? INT_MAX : nums2[i2 + k / 2 - 1];
		if (key1<key2) {
			return findKth(nums1, i1 + k / 2, nums2, i2, k - k / 2);
		}
		else {
			return findKth(nums1, i1, nums2, i2 + k / 2, k - k / 2);
		}
	}

};