<reponame>JunzhongLin/leetcode_practice
'''
Given an array arr of integers, check if there exists two integers N and M such that N is the double of M ( i.e. N = 2 * M).

More formally check if there exists two indices i and j such that :

i != j
0 <= i, j < arr.length
arr[i] == 2 * arr[j]


Example 1:

Input: arr = [10,2,5,3]
Output: true
Explanation: N = 10 is the double of M = 5,that is, 10 = 2 * 5.
Example 2:

Input: arr = [7,1,14,11]
Output: true
Explanation: N = 14 is the double of M = 7,that is, 14 = 2 * 7.
Example 3:

Input: arr = [3,1,7,11]
Output: false
Explanation: In this case does not exist N and M, such that N = 2 * M.

'''


class Solution:
    def checkIfExist(self, arr: List[int]) -> bool:

        visited = set()

        for i in range(0, len(arr)):
            if (arr[i] * 2 in visited) or (arr[i] / 2 in visited):
                return True
            else:
                visited.add(arr[i])
        return False

'''
Given an array arr of integers, check if there exists two integers N and M such that N is the double of M ( i.e. N = 2 * M).

More formally check if there exists two indices i and j such that :

i != j
0 <= i, j < arr.length
arr[i] == 2 * arr[j]


Example 1:

Input: arr = [10,2,5,3]
Output: true
Explanation: N = 10 is the double of M = 5,that is, 10 = 2 * 5.
Example 2:

Input: arr = [7,1,14,11]
Output: true
Explanation: N = 14 is the double of M = 7,that is, 14 = 2 * 7.
Example 3:

Input: arr = [3,1,7,11]
Output: false
Explanation: In this case does not exist N and M, such that N = 2 * M.

'''


class Solution:
    def checkIfExist(self, arr: List[int]) -> bool:

        visited = set()

        for i in range(0, len(arr)):
            if (arr[i] * 2 in visited) or (arr[i] / 2 in visited):
                return True
            else:
                visited.add(arr[i])
        return False
Given an array arr of integers, check if there exists two integers N and M such that N is the double of M ( i.e. N = 2 * M).  More formally check if there exists two indices i and j such that :  i != j 0 <= i, j < arr.length arr[i] == 2 * arr[j]   Example 1:  Input: arr = [10,2,5,3] Output: true Explanation: N = 10 is the double of M = 5,that is, 10 = 2 * 5. Example 2:  Input: arr = [7,1,14,11] Output: true Explanation: N = 14 is the double of M = 7,that is, 14 = 2 * 7. Example 3:  Input: arr = [3,1,7,11] Output: false Explanation: In this case does not exist N and M, such that N = 2 * M.