【leetcode】合并两个有序数组

题目：合并两个有序数组

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.Note:You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additional elements from nums2. The number of elements initialized in nums1 and nums2 are m and n respectively.

思路：从前往后排序的话，会涉及到数组元素多次移动，所以我们考虑从后往前进行排序

   void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {        int end=m+n-1;        m--;n--;        while(m>=0&&n>=0)        {            if(nums2[n]>nums1[m])            {                nums1[end--]=nums2[n--];            }            else            {                nums1[end--]=nums1[m--];            }        }        while(n>=0)        {            nums1[end--]=nums2[n--];        }    }};

更优的一种解法：

void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {         int i = m - 1, j = n - 1, tar = m + n - 1;        while (j >= 0) {            nums1[tar--] = i >= 0 && nums1[i] > nums2[j] ? nums1[i--] : nums2[j--];//i==0之后再不能继续减减了        }    }