《剑指Offer》-- 题目一：找出数组中重复的数字（Python多种方法实现）

def find_double_num(nums):
    """思路一：把输入的数组排序，从排序数组中找出重复的数字
    """
    nums_sorted = sorted(nums)
    length = len(nums_sorted)
    for i in range(1, length):
        if nums_sorted[i] == nums_sorted[i - 1]:
            print("重复数字: ", nums_sorted[i])
            return True
    return False

def find_double_num2(nums):
    """思路二：哈希表，从头到尾顺序扫描数组中的每个数字，
    哈希表中没有这个数字就加入哈希表。如果哈希表中存在就找到了一个重复的数字"""
    hash_map = dict()
    for i, val in enumerate(nums):
        if val in hash_map:
            print("重复数字: ", val)
            return True
        hash_map[val] = i
    return False

def find_double_num3(nums):
    if nums is None and len(nums) <= 0:
        return False
    for i in range(len(nums)):
        while i != nums[i]:
            if nums[i] == nums[nums[i]]:
                print("重复数字: ", nums[i])
                return True
            else:
                tmp = nums[i]
                nums[i] = nums[tmp]
                nums[tmp] = tmp
    return False

nums_test = [2, 3, 1, 0, 2, 5, 3]
print(find_double_num(nums_test))
print(find_double_num2(nums_test))
print(find_double_num3(nums_test))

重复数字:  2
True
重复数字:  2
True
重复数字:  2
True