Home / Questions / 391477
Accepted
Sebastian Parias
Asked: 2020-09-23 09:19:22 +0800 CST 2020-09-23 09:19:22 +0800 CST

twoSum program from leet code in Python

  • 772

Trying to do this problem in Python: https://leetcode.com/problems/two-sum/ ...I have the following doubt... So far the code I have is this.

class Solution:
def twoSum(self, nums, target: int):
    for i in nums:
        for j in nums:
            if i + j == target and nums.index(i) != nums.index(j):
                print (nums.index(i), nums.index(j))

Specifically, the problem is that when iterating with the for loops the list that is entered, assuming that the list has 2 equal elements, only the first element is iterated, due to the characteristics of the lists, but I need to iterate all the elements even if they are repeated . Is there any solution or am I misapproaching the problem?

lista

1 Answers

  1. Best Answer

    Here are some examples that may be useful to you. The latter executes in O(n), but the former in O(n^2):

    class Solution:
    def twoSum1(self, nums, target: int):
        for i in range(len(nums)):
            for j in range(i+1,len(nums)):
                if nums[i]+nums[j] == target:
                    return [i, j]
        return "No existen elementos que sumen "+str(target)
    
    def twoSum2(self, nums, target: int):
        diccionario={}
        for i in range(len(nums)):
            diferencia = target - nums[i]
            if diferencia in diccionario:
                return [diccionario[diferencia],i]
            else:
                diccionario[nums[i]] = i
        return "No existen elementos que sumen "+str(target)


solucion1 = Solution()

print("Primera solución:")
print(solucion1.twoSum1([2, 7, 11, 15], 9))
print(solucion1.twoSum1([3, 2, 4], 6))
print(solucion1.twoSum1([3,3], 6))

print("\nSegunda solución:")
print(solucion1.twoSum2([2, 7, 11, 15], 9))
print(solucion1.twoSum2([3, 2, 4], 6))
print(solucion1.twoSum2([3, 3], 6))

    The result in console is shown:

    Primera solución:
[0, 1]
[1, 2]
[0, 1]

Segunda solución:
[0, 1]
[1, 2]
[0, 1]
    • 0