Merge Sorted Array

Easy

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

One pass - O(n) time, O(1) space - (2ms, 100%)

``````class Solution {
public void merge(int[] nums1, int m, int[] nums2, int n) {
int k = m + n;
int i = m - 1;
int j = n - 1;
for (int l = k - 1; l >= 0; l--) {
// nums2[] elements have all been copied
if (j < 0) {
return;
}
// nums1[] elements have all been copied
if (i < 0) {
nums1[l] = nums2[j];
j--;
continue;
}

// compare and assign elements from nums1, nums2
if (nums2[j] > nums1[i]) {
nums1[l] = nums2[j];
j--;
} else {
nums1[l] = nums1[i];
i--;
}
}

}
}

// [1,2,3,0,0,0]
// [4,5,6]

// [4,5,6,0,0,0]
// [1,2,3]``````

Another more concise implementation (2ms, 100%)

``````class Solution {

public void merge(int[] nums1, int m, int[] nums2, int n) {
int k = m + n - 1;
int i = m - 1;
int j = n - 1;
while (i >= 0 && j>= 0) {
// compare and assign elements from nums1, nums2
if (nums2[j] > nums1[i]) {
nums1[k--] = nums2[j--];
} else {
nums1[k--] = nums1[i--];
}
}
while (j >= 0) {
nums1[k--] = nums2[j--];
}
}
}``````

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