Sum of Digits of String After Convert

Leetcode Problem:

• Sum of Digits of String After Convert

Summary

• This problem involves converting a string into an integer by replacing each letter with its position in the alphabet, then transforming the integer by summing its digits repeatedly k times.

Approach

• The approach used is to first convert the string into an integer by subtracting the ASCII value of 'a' from each character and adding 1
• Then, the integer is transformed by summing its digits using a helper function
• This process is repeated k times.

Complexity

• O(n*k) where n is the length of the string and k is the number of transformations.

Explain

• The solution code defines a class Solution with two methods: getSum and getLucky
• The getSum method takes a string as input and returns the sum of its digits
• The getLucky method takes a string and an integer as input and returns the resulting integer after performing the transformations
• The getLucky method first converts the string into an integer, then repeatedly transforms the integer by summing its digits using the getSum method
• The process is repeated k times, and the final result is returned.

Solution Code:

class Solution {
public:
    int getSum(string s){
        int sum = 0;
        for(int i = 0 ; i < s.size(); i++){
            sum += s[i] - '0';
        }
        return sum;
    }
    int getLucky(string s, int k) {
        string num = "";
        for(int i = 0 ; i < s.size(); i++){
            num += to_string(s[i] - 'a' + 1);
        }
        int transform;
        while(k--){
            transform = getSum(num);
            num = to_string(transform);
        }
        
        return transform;
    }
};