Dare2Solve
Given a string s
consisting of lowercase English letters, you first convert each letter to its position in the alphabet (e.g., 'a' -> 1
, 'b' -> 2
, etc.). Then you concatenate these numbers to form a single number. After that, you perform a transformation k
times where, in each transformation, you replace the number with the sum of its digits. The goal is to return the resulting number after k
transformations.
The problem requires two main operations:
The key observation is that the transformation reduces the number's size in each step, making it more manageable after a few iterations. The repetitive nature of summing digits is an indicator that the problem can be solved efficiently even with multiple iterations.
s
to its corresponding position in the alphabet. Concatenate these values to form a large number in string format.k
times, where each transformation involves summing the digits of the current number and updating the number to this sum.k
transformations, the number will be reduced to a single-digit or small number, which is returned as the final result.s
to its numeric form is O(n)
, where n
is the length of s
.O(m)
, where m
is the number of digits in the current number. Given k
transformations, the total complexity is O(n + k * m)
.O(1)
if we consider only the extra space for storing numeric values, since all operations are done in place (excluding the input and output).
class Solution {
public:
int getLucky(string s, int k) {
string value = "";
for (char c : s) {
value += to_string(c - 'a' + 1);
}
while (k-- > 0) {
int v = 0;
for (char c : value) {
v += c - '0';
}
value = to_string(v);
}
return stoi(value);
}
};
class Solution:
def getLucky(self, s: str, k: int) -> int:
value = ''.join(str(ord(c) - 96) for c in s)
while k > 0:
v = sum(int(digit) for digit in value)
value = str(v)
k -= 1
return int(value)
class Solution {
public int getLucky(String s, int k) {
StringBuilder value = new StringBuilder();
for (char c : s.toCharArray()) {
value.append(c - 'a' + 1);
}
while (k-- > 0) {
int v = 0;
for (char c : value.toString().toCharArray()) {
v += Character.getNumericValue(c);
}
value = new StringBuilder(String.valueOf(v));
}
return Integer.parseInt(value.toString());
}
}
var getLucky = function (s, k) {
let value = '';
for (i = 0; i < s.length; i++) {
value += s.charCodeAt(i) - 96
}
do {
let v = 0
for (i = 0; i < value.length; i++)
v += Number(value[i])
value = v.toString();
k--;
} while (k > 0);
return value;
};