Python|列表中的三元素总和

获得导致特定解决方案的对数的问题已被多次处理，本文旨在将其扩展到 3 个数字，并讨论可以解决此特定问题的几种方法。让我们讨论可以执行此操作的某些方式。
方法#1：使用嵌套循环
这是可以解决这个特定问题的简单方法，并采用外部循环对每个元素进行迭代，内部循环检查剩余的差异，并将对添加到结果中。

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))

输出 ：

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

方法 #2：使用 itertools.combination()
这个特殊问题也可以使用函数的内置函数以简洁的方式完成。组合函数查找采用 K 个参数导致特定总和的所有组合。

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))

输出 ：

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

方法#3：使用 itertools.combination() 和额外的检查来提高 1000 个项目的运行时间。此外，它只检查是否存在匹配，如果找到匹配则输出组合。

Python3

import itertools
 
def solve(nums, k):
  # rule out cases where no of elements are less then 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("-----------------------------------------")

输出 ：

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
-----------------------------------------