洛谷P1030 [NOIP2001 普及组] 求先序排列 Python题解

原题链接

这题的读入非常坑，文件末尾存在r，因此读入时需要将其转换为列表再遍历。
或者也可以直接给print的输出加个特判。

转为列表

def dfs(mid, bw):
    ch = bw[-1]
    pos = -1
    for i in range(0, len(mid)):
        if mid[i] == ch:
            pos = i
            break
    if pos != -1:
        print(ch, end="")
        if mid[:pos]:
            dfs(mid[:pos], bw[:pos])
        if mid[pos + 1 :]:
            dfs(mid[pos + 1 :], bw[pos : len(bw) - 1])


s1 = input()
s2 = input()
ss1 = list(s1)
ss2 = list(s2)
ss1[-1] = ""
ss2[-1] = ""
dfs(ss1, ss2)

特判

def dfs(mid, bw):
    ch = bw[-1]
    pos = -1
    for i in range(0, len(mid)):
        if mid[i] == ch:
            pos = i
            break
    if pos != -1:
        if ch!='n' and ch!='r':
            print(ch, end="")
        if mid[:pos] != "":
            dfs(mid[:pos], bw[:pos])
        if mid[pos + 1 :] != "":
            dfs(mid[pos + 1 :], bw[pos : len(bw) - 1])


s1 = input()
s2 = input()
s1.replace("n", "")
s1.replace("r", "")
s2.replace("n", "")
s2.replace("r", "")
dfs(s1, s2)