# Code Signal – 共用字符数(commonCharacterCount)

## Objective

Given two strings, find the number of common characters between them.

Example

For `s1 = "aabcc"` and `s2 = "adcaa"`, the output should be `commonCharacterCount(s1, s2) = 3`.

Strings have `3` common characters – `2` “a”s and `1` “c”.

Input/Output

• [execution time limit] 4 seconds (py3)
• [input] string s1A string consisting of lowercase English letters.Guaranteed constraints:
`1 ≤ s1.length < 15`.
• [input] string s2A string consisting of lowercase English letters.Guaranteed constraints:
`1 ≤ s2.length < 15`.

## Walkthrough

My idea for this was very simple – change the provided strings to lists, and then go through them and count the common characters, let’s look at an example:

• We get two strings
• `s1 = "aabcc"`
• `s2 = "adcaa"`
• Next we convert them to lists
• `s1_list = ['a', 'a', 'b', 'c', 'c']`
• `s2_list = ['a', 'd', 'c', 'a', 'a']`
• And create a counter `common=0`
• Then we iterate through the the first list `s1_list`
• check if the character ‘a’ exists in the `s2_list`
• if so, we add + 1 to the counter,
• and delete the common character from the `s2_list`
• At the end we return the counter variable `common`

class Solution:
def commonCharacterCount(s1, s2):
s1_list = list(s1)
s2_list = list(s2)
print(s1_list)
print(s2_list)
common_count = 0

for i in s1_list:
for j in s2_list:
if i == j:
common_count += 1
s2_list.remove(j)
break
print(common_count)