leetcode-4-Median of Two Sorted Arrays

4. Median of Two Sorted Arrays

题目：

There are two sorted arrays nums1 and nums2 of size m and n respectively.
Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).
Example1:

nums1 = [1, 3]
nums2 = [2]
The median is 2.0

Example2:

nums1 = [1, 2]
nums2 = [3, 4]
The median is (2 + 3)/2 = 2.5

解法一

解析

用一个新数组存放nums1和nums2合并后的数组。有序数组的合并最后取出中位数

还有种思路，就是遍历两个数组，在里面找到第i个大元素，但是时间复杂度为O（m+n）

代码（C++）

class Solution {
public:
    double findMedianSortedArrays(vector& nums1, vector& nums2) {
        vector numsAll;

        for (int i = 0, j = 0; i < nums1.size() || j < nums2.size();) {
            if (i < nums1.size()) {
                if (j < nums2.size()) {
                    if (nums1[i] < nums2[j]) {
                        numsAll.push_back(nums1[i++]);
                    } else {
                        numsAll.push_back(nums2[j++]);
                    }
                } else {
                    numsAll.push_back(nums1[i++]);
                }
            } else {
                numsAll.push_back(nums2[j++]);
            }
        }

        int middle = (nums1.size() + nums2.size()) >> 1;
        if ((nums1.size() + nums2.size()) % 2 == 1) {
            return (double)numsAll[middle];
        } else {
            return ((double)numsAll[middle] + (double)numsAll[middle-1]) / 2.0;
        }

    }
};