# 88. Merge Sorted Array

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.

Note:

  • The number of elements initialized in nums1 and nums2 are m and n respectively.
  • You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additional elements from nums2.

Example:

Input:
nums1 = [1,2,3,0,0,0], m = 3
nums2 = [2,5,6],       n = 3

Output: [1,2,2,3,5,6]

# Solution

Approach 1: Two pointers.

# Code (Python)

Approach 1:

    def merge(self, nums1, m, nums2, n):
        """
        :type nums1: List[int]
        :type m: int
        :type nums2: List[int]
        :type n: int
        :rtype: void Do not return anything, modify nums1 in-place instead.
        """
        p1, p2, fill = m - 1, n - 1, m + n - 1
        while p1 >= 0 and p2 >= 0:
            if nums1[p1] >= nums2[p2]:
                nums1[fill] = nums1[p1]
                p1 -= 1
            else:
                nums1[fill] = nums2[p2]
                p2 -= 1
            fill -= 1
        while p2 >= 0:
            nums1[fill] = nums2[p2]
            p2 -= 1
            fill -= 1

# Code (C++)

Approach 1:

class Solution {
public:
    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
        int p1 = m - 1;
        int p2 = n - 1;
        int p3 = m + n - 1;
        while (p1 >=0 || p2 >= 0)
        {
            if (p2 < 0 || (p1 >= 0 && nums1[p1] > nums2[p2]))
            {
                nums1[p3] = nums1[p1];
                p1--;
            }
            else
            {
                nums1[p3] = nums2[p2];
                p2--;
            }
            p3--;
        }
    }
};