您的答案為: (())
正確答案為: 

用ideone跑 結果跟測資一樣
是換行的問題?

python code:

import sys
def dfs(step,n,a,left,right):
    if step == n:
        if left == right:
            str1 = ''.join(a)
            print(str1)
        return
    c = ['(',')']
    if left > right:
        for i in range(len(c)):
            a.append(c[i])
            if i == 0:
                dfs(step + 1,n,a,left + 1,right)
            else:
                dfs(step + 1,n,a,left,right + 1)
            a.pop()
        return
    else:
        a.append('(')
        dfs(step + 1,n,a,left + 1,right)
        a.pop()
        return
    return
while True:
    try:
        n = int(input())
        a = ['(']
        left = 1
        right = 0
        dfs(1,n * 2,a,left,right)
        print()
    except: break