[Array]Merge Sorted Array

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.

方法1： 开辟新数组进行归并操作。额外的存储空间为O(m+n)；

class Solution {public:    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {        vector<int> res ;        int i=0,j=0;        while(i<m&&j<n){            if(nums1[i]<nums2[j]){                res.push_back(nums1[i]);                i++;            }            else{                res.push_back(nums2[j]);                j++;            }        }        while(i<m){            res.push_back(nums1[i]);            i++;        }        while(j<n){            res.push_back(nums2[j]);            j++;        }        nums1=res;    }};

方法2： 因为nums1数组有足够的空间，所以利用这点从尾部开始从大到小进行排序。额外的存储空间为O(1)。

class Solution {public:    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {        int i = m - 1;        int j = n - 1;        int k = m + n - 1;        while(i>=0&&j>=0){            if(nums1[i]>nums2[j]){                nums1[k--]=nums1[i--];            }            else{                nums1[k--]=nums2[j--];            }        }        while(j>=0){            nums1[k--]=nums2[j--];        }    }};