文章标题1

MAIN()
    //归并排序
     MergeSort(a,0,num-1,tmp)
for i = 0 to num-1
    //二分查找
    ans = BinarySearch( a, X-a[i], num )

//归并排序伪代码
MERGESORT(A, p, r)
    if p < r
        q = (p + r) / 2
        MERGE_SORT(A, p, q)
        MERGE_SORT(A, q + 1, r)
        MERGE(A, p, q, r)

//二分查找伪代码
BINARYSEARCH(a,key,n)
while low <= high
    mid = (low + high)/2;
    if a[mid] == key
        return true
    else if key < a[mid]
        high = mid - 1
    else
        low = mid + 1
return false