//双指针注意指针移动情况。有序数组比较尾部数据即可;
public static void merge(int A[], int m, int B[], int n) {
int[] ints = Arrays.copyOf(A, m + n);
A=ints;
int index=m+n-1;
m--;
n--;
while (m>=0&&n>=0){
if (A[m]>B[n]){
A[index]=A[m];
m--;
}else {
A[index]=B[n];
n--;
}
index--;
}
while (n>=0){
A[index]=B[n];
n--;
index--;
}
}