[leetcode] Merge Sorted Array 直接插入排序法解題

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 (size that is greater or equal to m + n) to hold additional elements from B. The number of elements initialized in A and B are m andn respectively.

直接插入排序的 Java實現

說明：剛好複習了直接插入排序時看到這道題，可用直接插入排序解，思路爲先合併A,B兩個數組，然後排序即可，但這並不是好的方法。

/*用插入排序做，先合併兩個數組*/
public class Solution {
    public void merge(int A[], int m, int B[], int n) {
        for(int i = m,j = 0 ; i < m+n && j < n; i++)
			 A[i] = B[j++];
		 InsertSort(A, m+n);
    }
    
    public  void InsertSort(int a[], int m)
	{
		int i,j,k,temp;
		for(i = 1 ; i < m ; i++)
		{
			for( j = i-1 ; j >=0 ;j --)
				if(a[j] < a[i])
					break;  
			if( j !=i -1 )   
			{
				temp = a[i];
				for( k = i-1 ; k >j ;k--)
				{
					a[k+1] = a[k];
				}
				a[k+1] = temp;
			}
		}
	}
}

另：比較好的方法是從A尾部開始插入

public void merge(int A[], int m, int B[], int n) {
        int i = m - 1, j = n - 1, k;
		for (k = m + n - 1; k >= 0; k--)
		{
			if (i >= 0 && (j < 0 || A[i] > B[j]))
			{
				A[k] = A[i--];
			} else
			{
				A[k] = B[j--];
			}
		}
    }