[LeetCode] Merge Sorted Array

Given two sorted integer arrays A and B, merge B into A as one sorted array.

Note:
You may assume that A has enough space to hold additional elements from B. The number of elements initialized in A and B are m and n respectively.

考慮從后往前比較，這樣就不會產生需要數據后移的問題了。時間復雜度O(n+m)

class Solution {
public:
    void merge(int A[], int m, int B[], int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int index = m + n - 1;
        int aIndex = m - 1;
        int bIndex = n - 1;
        while(0 <= aIndex && 0 <= bIndex)
        {
            if (B[bIndex] > A[aIndex])
            {
                A[index--] = B[bIndex--];
            }
            else
            {
                A[index--] = A[aIndex--];
            }
        }
        
        while(0 <= aIndex)
        {
            A[index--] = A[aIndex--];
        }
        
        while(0 <= bIndex)
        {
            A[index--] = B[bIndex--];
        }
    }
};