004. Median of Two Sorted Arrays

 1 class Solution {
 2 public:
 3     double findMedianSortedArrays(vector<int>& nums1, vector<int>& nums2) {
 4         const int m = nums1.size();
 5         const int n = nums2.size();
 6         int total = m + n;
 7         if (total & 0x1) return find_kth(nums1.begin(), m, nums2.begin(), n, total / 2 + 1);
 8         else 
 9             return double(find_kth(nums1.begin(), m, nums2.begin(), n, total / 2) + 
10                           find_kth(nums1.begin(), m, nums2.begin(), n, total / 2 + 1)) / 2;
11     }
12 //private：
13     int find_kth(vector<int>::const_iterator iter1, int len1, vector<int>::const_iterator iter2, int len2, int count)
14     {
15         if (len1 > len2) { // 这里比较重要
16             return find_kth(iter2, len2, iter1, len1, count);
17         }
18         else {
19             if (len1 == 0) return *(iter2 + count - 1);
20             if (count == 1) return min(*iter1, *iter2);
21             int m = min(len1, count / 2); // 这里的判定条件
22             int n = count - m;
23             if (*(iter1 + m - 1) < *(iter2 + n - 1)) return find_kth(iter1 + m, len1 - m, iter2, len2, count - m);
24             else if (*(iter1 + m - 1) > *(iter2 + n - 1)) return find_kth(iter1, len1, iter2 + n, len2 - n, count - n);
25             else return *(iter1 + m - 1);
26         }
27     }
28 };