Skip to content
Related Articles

Related Articles

Python | Three element sum in list

View Discussion
Improve Article
Save Article
  • Last Updated : 08 Sep, 2022
View Discussion
Improve Article
Save Article

The problem of getting the number of pairs that lead to a particular solution has been dealt with many times, this article aims at extending that to 3 numbers and discussing several ways in which this particular problem can be solved. Let’s discuss certain ways in which this can be performed.
Method #1: Using Nested loops
This is the naive method in which this particular problem can be solved and takes the outer loop to iterate for each element and the inner loop checks for the remaining difference adding the pairs to the result.
 

Python3




# Python3 code to demonstrate
# 3 element sum
# using nested loops
 
# initializing list
test_list = [4, 1, 3, 2, 6, 5]
 
# initializing sum
sum = 9
 
# printing original list
print("The original list : " + str(test_list))
 
# using nested loops
# 3 element sum
res = []
for i in range(0, len(test_list)-2):
    for j in range(i + 1, len(test_list)-1):
        for k in range(j + 1, len(test_list)):
            if test_list[i] + test_list[j] + test_list[k] == sum:
                temp = []
                temp.append(test_list[i])
                temp.append(test_list[j])
                temp.append(test_list[k])
                res.append(tuple(temp))
 
# print result
print("The 3 sum element list is : " + str(res))

Output : 

The original list : [4, 1, 3, 2, 6, 5]
The 3 sum element list is : [(4, 3, 2), (1, 3, 5), (1, 2, 6)]

 

 
Method #2 : Using itertools.combination() 
This particular problem can also be done in a concise manner using the inbuilt function of a function. The combination function finds all the combinations taking K arguments leading to a particular sum. 
 

Python3




# Python3 code to demonstrate
# 3 element sum
# using itertools.combination()
from itertools import combinations
 
# function to get the sum
def test(val):
    return sum(val) == 9
 
# initializing list
test_list = [4, 1, 3, 2, 6, 5]
 
# initializing sum
summation = 9
 
# printing original list
print("The original list : " + str(test_list))
 
# using itertools.combination()
# 3 element sum
res = list(filter(test, list(combinations(test_list, 3))))
 
# print result
print("The 3 sum element list is : " + str(res))

Output : 

The original list : [4, 1, 3, 2, 6, 5]
The 3 sum element list is : [(4, 3, 2), (1, 3, 5), (1, 2, 6)]

 

Method #3: Using itertools.combination() and additional check to improve runtime for 1000 items. also, it only checks if a match exists or not, if a match is found then output the combination.

Python3




import itertools
 
def solve(nums, k):
  # rule out cases where no of elements are less than 3
  if len(nums)<=2:
    return False
  else:
    # get all unique combinations
    permut = itertools.combinations(nums, 3)
 
    #rule out the loop if even the max * 3 < target
    max_value = max(nums)
    if max_value*3 < k:
      return False
    else:
      #check until a match is found
      for i in permut:
        if i[0]+i[1]+i[2]==k:
          return True
        return False
  
nums = [4,1,3,1]
k=5
print("Test case :-\nk=",k," \nnums = ",nums)
print("-----------------------------------------")
Solution.solve(nums, k)
print("-----------------------------------------")
 
nums = [2, 4, 3, 0, 1]
k = 0
print("Test case :-\nk=",k," \nnums = ",nums)
print("-----------------------------------------")
Solution.solve(nums, k)
print("-----------------------------------------")
 
nums = [0]
k = 0
print("Test case :-\nk=",k," \nnums = ",nums)
print("-----------------------------------------")
Solution.solve(nums, k)
print("-----------------------------------------")
 
nums = [1, 0]
k = 1
print("Test case :-\nk=",k," \nnums = ",nums)
print("-----------------------------------------")
Solution.solve(nums, k)
print("-----------------------------------------")
 
nums = [2, 0, 1]
k = 3
print("Test case :-\nk=",k," \nnums = ",nums)
print("-----------------------------------------")
Solution.solve(nums, k)
print("-----------------------------------------")
 
nums = [13, 76, 35, 89, 15, 76, 54, 4, 66, 4,
        9, 25, 9, 48, 26, 76, 95, 80, 19, 66,
        74, 15, 18, 96, 36, 78, 80, 42, 42, 76,
        85, 74, 96, 9, 95, 29, 58, 43, 57, 14,
        38, 21, 55, 56, 18, 25, 3, 11, 76, 77,
        72, 36, 44, 88, 93, 2, 95, 86, 77, 47,
        3, 51, 34, 46, 70, 90, 4, 24, 58, 6, 91,
        93, 59, 69, 89, 5, 58, 87, 23, 15, 98, 24,
        62, 64, 15, 43, 93, 68, 17, 4, 78, 6, 2,
        10, 52, 17, 28, 82, 20, 44, 78, 91, 1, 79,
        17, 23, 27, 66, 88, 57, 60, 78, 68, 6,
        35, 43, 73, 37, 12, 22, 47, 59, 40, 36,
        0, 70, 91, 68, 33, 54, 44, 78, 23, 69, 60,
        44, 32, 15, 20, 28, 36, 55, 73, 12, 55, 26,
        43, 57, 63, 46, 0, 43, 24, 91, 86, 61, 15,
        10, 29, 8, 51, 84, 94, 18, 5, 63, 90, 4,
        38, 28, 84, 67, 18, 33, 85, 93, 31, 38,
        97, 14, 79, 11, 92, 3, 8, 27, 65, 39, 1,
        83, 38, 8, 83, 53, 53, 44, 57, 64, 78, 1,
        44, 72, 100, 86, 85, 16, 5, 27, 24, 2, 56,
        74, 16, 90, 65, 8, 93, 64, 72, 45, 47, 7,
        83, 100, 99, 62, 89, 38, 38, 42, 98, 18,
        29, 88, 48, 35, 0, 82, 56, 22, 64, 13, 54,
        66, 32, 9, 2, 52, 80, 28, 19, 9, 38, 98, 38,
        21, 41, 65, 78, 63, 97, 71, 99, 41, 89, 78,
        48, 47, 72, 67, 79, 45, 43, 92, 30, 28, 42,
        52, 56, 24, 46, 55, 82, 22, 86, 67, 43, 84,
        41, 26, 66, 26, 32, 8, 93, 65, 10, 47, 19,
        70, 84, 43, 99, 74, 78, 51, 59, 58, 38, 75,
        86, 24, 48, 27, 72, 32, 15, 28, 98, 11, 70,
        74, 91, 89, 90, 74, 69, 60, 78, 6, 67, 34,
        100, 70, 98, 70, 60, 12, 58, 26, 21, 44, 64,
        15, 82, 81, 52, 9, 82, 94, 99, 43, 22, 14,
        16, 27, 68, 72, 69, 45, 60, 10, 91, 31, 58, 91,
        71, 42, 19, 43, 42, 80, 61, 50, 2, 81, 45, 40,
        44, 100, 68, 74, 19, 0, 33, 24, 58, 59, 1, 26,
        65, 69, 19, 60, 12, 50, 82, 44, 18, 96, 77, 43,
        33, 31, 53, 9, 36, 86, 24, 46, 11, 26, 3, 43, 8,
        42, 17, 55, 60, 56, 33, 66, 90, 64, 42, 73,
        61, 34, 13, 43, 9, 59, 46, 0, 68, 93, 60, 78,
        92, 76, 45, 20, 31, 47, 21, 44, 2, 23, 78, 72,
        62, 65, 56, 26, 80, 65, 87, 61, 88, 22, 38, 70,
        98, 48, 25, 95, 55, 3, 32, 28, 50, 13, 57, 18,
        95, 11, 23, 57, 21, 93, 35, 38, 75, 79, 39, 87,
        30, 95, 73, 37, 47, 43, 15, 73, 59, 0, 29, 29,
        30, 50, 13, 73, 1, 32, 7, 46, 7, 24, 43, 21, 84,
        1, 6, 96, 33, 69, 2, 70, 98, 2, 90, 31, 66, 74, 58, 66, 56, 33,
        5, 78, 19, 21, 98, 76, 1, 55, 97, 39, 43, 43, 44, 7, 61, 84, 31,
        0, 67, 46, 39, 23, 7, 31, 29, 2, 71, 7, 35, 60, 20, 94, 23, 81,
        40, 79, 11, 46, 71, 25, 42, 54, 10, 21, 11, 72, 86, 48, 53, 67,
        36, 55, 49, 98, 65, 37, 27, 63, 20, 86, 60, 29, 63, 75, 91, 30,
        55, 23, 82, 88, 53, 62, 44, 25, 27, 99, 39, 4, 40, 41, 35, 35, 61,
        62, 10, 98, 9, 82, 21, 39, 82, 89, 41, 71, 26, 51, 2, 73, 30, 49,
        92, 16, 66, 60, 68, 2, 99, 91, 15, 77, 43, 44, 46, 69, 79, 100, 47,
        9, 66, 33, 25, 15, 5, 77, 86, 81, 82, 69, 10, 0, 98, 4, 90, 30, 89,
        87, 83, 97, 35, 96, 71, 15, 50, 12, 82, 79, 91, 79, 28, 62, 24, 75,
        77, 68, 59, 87, 29, 81, 66, 92, 85, 4, 17, 48, 69, 28, 37, 55, 39,
        11, 92, 57, 26, 64, 91, 44, 37, 3, 44, 57, 13, 75, 21, 39, 17, 29,
        18, 74, 43, 93, 53, 6, 61, 71, 89, 99, 13, 92, 23, 99, 18, 13, 38,
        14, 9, 82, 10, 7, 41, 24, 40, 61, 42, 26, 2, 43, 38, 3, 50, 43, 75,
        47, 95, 16, 41, 40, 43, 14, 26, 40, 79, 11, 30, 16, 39, 46, 45, 25,
        44, 79, 21, 48, 48, 23, 38, 79, 62, 71, 8, 53, 12, 72, 64, 71, 50,
        90, 38, 77, 6, 48, 74, 77, 53, 85, 82, 19, 18, 43, 97, 67, 56, 25,
        46, 87, 27, 99, 21, 13, 56, 71, 87, 73, 25, 0, 52, 82, 18, 65, 34,
        96, 33, 99, 43, 45, 2, 59, 29, 53, 34, 78, 27, 41, 74, 74, 59, 96,
        74, 45, 74, 44, 28, 62, 4, 90, 62, 31, 89, 72, 88, 69, 5, 29, 26,
        81, 66, 96, 53, 87, 72, 89, 9, 30, 71, 75, 83, 46, 71, 57, 12, 77,
        24, 44, 71, 34, 42, 11, 67, 9, 69, 47, 95, 93, 72, 12, 40, 98, 83,
        25, 27, 91, 21, 31, 0, 44, 56, 1, 76, 30, 100, 18, 46, 35, 72, 61,
        39, 90, 25, 78, 42, 77, 13, 72, 32, 3, 84, 63, 59, 100, 60, 22, 57,
        50, 40, 63, 65, 2, 27, 88, 63, 40, 97, 94, 69, 72, 98, 2, 68, 13,
        62, 76, 97, 14, 36, 15, 91, 80, 55, 45, 67, 50, 13, 49, 54, 72,
        84, 36, 69, 74, 35, 30, 47, 64, 91, 24, 16, 41, 41, 19, 96, 25,
        38, 60, 43, 86, 6, 23, 81, 71, 73, 56, 12, 44, 67, 28, 39, 1,
        52, 40, 28, 45, 44, 53, 63, 7, 66, 45, 44, 68, 6, 98, 100, 95]
k = 787
 
print("Test case :-\nk=",k," \nnums = ",nums[0:10],".....")
print("-----------------------------------------")
Solution.solve(nums, k)
print("-----------------------------------------")
 
nums = [0, 0, 0]
k = 0
print("Test case :-\nk=",k," \nnums = ",nums)
print("-----------------------------------------")
Solution.solve(nums, k)
print("-----------------------------------------")

Output : 

Test case :-
k= 5  
nums =  [4, 1, 3, 1]
-----------------------------------------
Found match :  (1, 3, 1) 5
-----------------------------------------
Test case :-
k= 0  
nums =  [2, 4, 3, 0, 1]
-----------------------------------------
Match not found.
-----------------------------------------
Test case :-
k= 0  
nums =  [0]
-----------------------------------------
Match not found.
-----------------------------------------
Test case :-
k= 1  
nums =  [1, 0]
-----------------------------------------
Match not found.
-----------------------------------------
Test case :-
k= 3  
nums =  [2, 0, 1]
-----------------------------------------
Found match :  (2, 0, 1) 3
-----------------------------------------
Test case :-
k= 787  
nums =  [13, 76, 35, 89, 15, 76, 54, 4, 66, 4] .....
-----------------------------------------
Match not found.
-----------------------------------------
Test case :-
k= 0  
nums =  [0, 0, 0]
-----------------------------------------
Found match :  (0, 0, 0) 0
-----------------------------------------

My Personal Notes arrow_drop_up
Recommended Articles
Page :

Start Your Coding Journey Now!