# Python: Find a pair of elements from a given array whose sum equals a specific target number

## Python Class: Exercise-5 with Solution

Write a Python class to find a pair of elements (indices of the two numbers) from a given array whose sum equals a specific target number.

* Difficulty: Medium. Company: Google, Facebook*

**Sample Solution-1:**

**Python Code:**

```
class py_solution:
def twoSum(self, nums, target):
lookup = {}
for i, num in enumerate(nums):
if target - num in lookup:
return (lookup[target - num], i )
lookup[num] = i
print("index1=%d, index2=%d" % py_solution().twoSum((10,20,10,40,50,60,70),50))
```

Sample Output:

index1=2, index2=3

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**Flowchart:**

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**Sample Solution-2:**

**Python Code:**

```
class py_solution(object):
def twoSum(self, nums, target_num):
"""
:type nums: list[int]
:type target: int
:return type: list[int]
"""
result_dict = dict()
pos = 0
while pos < len(nums):
if (target_num - nums[pos]) not in result_dict:
result_dict[nums[pos]] = pos
pos += 1
else:
return [result_dict[target_num - nums[pos]], pos]
print(py_solution().twoSum([10,20,10,40,50,60,70],50))
print(py_solution().twoSum([10,20,10,40,50,60,70],52))
```

Sample Output:

[2, 3] None

**Flowchart:**

## Visualize Python code execution:

The following tool visualize what the computer is doing step-by-step as it executes the said program:

**Python Code Editor:**

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**Previous:** Write a Python class to get all possible unique subsets from a set of distinct integers.

**Next:** Write a Python class to find the three elements that sum to zero from a set (array) of n real numbers.

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## Python: Tips of the Day

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