88. Merge Sorted Array

Sort

class Solution {
public:
    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
        for (int i = 0; i < n; ++i) {
            nums1[m + i] = nums2[i];
        }
        sort(nums1.begin(), nums1.end());
    }
};

• T: $O(N \cdot \log N)$
• S: $O(N)$

Two Pointers

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

• T: $O(N + M)$
• S: $O(M)$