Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.
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 equal to m + n) to hold additional elements from nums2.
Input: nums1 = [1,2,3,0,0,0], m = 3, nums2 = [2,5,6], n = 3
Output: [1,2,2,3,5,6]
Input: nums1 = [1], m = 1, nums2 = [], n = 0
Output: [1]
0 <= n, m <= 200
1 <= n + m <= 200
nums1.length == m + n
nums2.length == n
-109 <= nums1[i], nums2[i] <= 109
Solutions (Click to expand)
We can modify the nums1 array in place by merging the number of nums2 and nums1 (starting from m - 1) from back to front or greatest to least. Since you there are enough 0s at the end of the nums1 array to fit all the numbers of nums2 we are able to have a pointer i that starts at the end of that nums1 and can point to where the next sorted number can be placed. We will have to other pointers, m and n, that will point to the ends of the nums1 and nums2 (for the case of nums1, the end of the array is at index m - 1). The greater number of the two pointers will be taken and placed at index i of nums1. Pointers will decrement and the operations will repeat until one pointer reaches the end of their array. If there are still numbers in the nums2 array we can insert the rest of the elements into nums1.
1.
[1,2,3,0,0,0]
^ ^
[2,5,6]
^
--------------------
2.
[1,2,3,0,0,6]
^ ^
[2,5,6]
^
--------------------
3.
[1,2,3,0,5,6]
^ ^
[2,5,6]
^
--------------------
4.
[1,2,3,3,5,6]
^ ^
[2,5,6]
^
--------------------
5.
[1,2,2,3,5,6]
^ ^
[2,5,6]
^