一组无序的自然数集合，由0,1,2... ...,n的数字和一个的数字X（X>=0 && X<=n）组成，请从集合中找出这个重复数字X。

a = input()
b = a.split(" ")
c = []
for i in b:
    for j in c:
        if i == j:
            print (i)
    c.append(i)

指针排序

def sort_list(a):
    first = 0
    second = 1
    while first < len(a)-1:
        if a[first] > a[second]:
            temp = a[first]
            a[first] = a[second]
            a[second] = temp
            if first>0:
                first -= 1
                second -= 1
        else:
            first += 1
            second += 1
    return a

a = list(map(int,input().split(" ")))
print (sort_list(a))

二分查找

def find_num(a,b):
    first = 0
    end = len(a)
    num = (first+end)//2
    while num!=first and num!=end:
        num = (first+end)//2
        print(num, first, end)
        if int(b) < int(a[num]):
            end = num
        else:
            first = num
        num = (first+end)//2
        print(num, first, end)
    if a[num] == b:
        print(b)
    else:
        print("not exist!")

a = [1, 3, 4, 6, 8, 9]
b = 2
find_num(a,b)

递归查找

def find_num(a,b):
    print(a)
    if len(a)==1:
        if a[0]==b:
            print("Find!")
            return
        else:
            print("Not find!")
            return
    else:
        num = len(a)//2
        if a[num] == b:
            print("Find!")
            return a[num]
        elif a[num]<b:
            c = find_num(a[num:],b)
            return c
        else:
            c = find_num(a[0:num],b)
            return c

a = [1, 3, 4, 6, 8, 9]
b = 1
c=find_num(a,b)
print(c)

二叉树插入和中序输出

class Tree():
    def __init__(self, value):
        self.root = value
        self.left = None
        self.right = None

    def insert(self, value):
        self.insert_node(self,value)
        
    def insert_node(self, root_node, v):
        if v < root_node.root:
            if root_node.left == None:
                root_node.left = Tree(v)
            else:
                self.insert_node(root_node.left, v)
        else: 
            if root_node.right == None:
                root_node.right = Tree(v)
            else:
                self.insert_node(root_node.right, v)
                
result = []
def print_tree(node):
    if node.left != None:
        print_tree(node.left)
    result.append(node.root)
    if node.right != None:
        print_tree(node.right)
        
n1 = Tree(5)
n1.insert(7)
n1.insert(3)
n1.insert(1)

print(n1.root,n1.left.root,n1.right.root)
print(n1.left.root,n1.left.left.root,n1.left.right)
print_tree(n1)
print(result)