https://leetcode.com/problems/sum-of-digits-of-string-after-convert/
Source
int getLucky(string s, int k) {
string strNums;
FOR (i, s.length()) {
const int n = s[i] - 'a' + 1;
strNums += to_string(n);
}
int ans = 0;
FOR (i, k) {
int sum = 0;
FOR (j, strNums.length()) {
sum += strNums[j] - '0';
}
ans = sum;
strNums = to_string(ans);
}
return ans;
}