[Python] Programming to find the number of a in a character string that repeats a specified number of times.

[Python] Programming to find the number of a in a character string that repeats a specified number of times

▼ Question

--list gives a string of arbitrary length (s) --Gives the number of characters. (n) --Calculate the number of a contained in repeating s until the number of characters (n) is satisfied.

URL

▼sample input

python

s ="aba"
n =10

▼sample output

python

7

image

abaabaabaa <-7 a

▼my answer

python

def repeatedString(s, n):
    a = s.count("a")
    ans=i=0    
    
    #Find the number of a contained in the surplus characters
    r = n%len(s)
    if r!=0:
        while i<r:
            if s[i]=="a":
                ans += 1
            i+=1
            
    ans += a*int(n/len(s)) 
    return ans    
            

if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')
    s = input()
    n = int(input())
    result = repeatedString(s, n)
    fptr.write(str(result) + '\n')
    fptr.close()

--For to extract elements from a fixed object --While to repeat until the specified condition is met

Replace while with for

def repeatedString(s, n):
    a = s.count("a")
    ans=0    
    
    #Find the number of iterations(math.do not use floor)
    r = n%len(s)
    if r!=0:
        for i in range(r):
            if s[i]=="a":
                ans += 1
            
    ans += a*int(n/len(s)) 
    return ans    
            
repeatedString(s, n)

▼ Processing

--Extract the element from the surplus character number sentence list s, and create a list that stores 1 for a and 0 for other cases. --Add 1 with sum (list).

Comprehension notation

def repeatedString(s, n):
    a = s.count("a")
    ans=0    
    
    #Find the number of iterations(math.do not use floor)
    r = n%len(s)
    if r!=0:
        ans =  sum([(1 if s[i]=="a" else 0) for i in range(r)])
             
    ans += a*int(n/len(s)) 
    return ans    
            
repeatedString(s, n)

Supplement: MemoryError

I created a repeated character string for the specified number of characters and counted the number of a from it, but when the number is large, a Memory Error occurs.

python

s ="babbaabbabaababaaabbbbbbbababbbabbbababaabbbbaaaaabbaababaaabaabbabababaabaabbbababaabbabbbababbaabb"
n = 860622337747

▼ The process of finding a character string is heavy.

python

def repeatedString(s, n):
    #Advance (math).floor is not used)
    if float(n/len(s)):
        r = int(n/len(s)) +1
    else:
        r = n/len(s)
    
    #Ask for a string
    ans = x = 0
    ss = s*r
    for letter in ss:
        x += 1
        if x>n:
            break
        elif letter == "a":
            ans += 1
    return ans
            
repeatedString(s, n)

#MemoryError: