Calculate Digit Sum of a String
Python solution:
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 class Solution:
def digitSum(self, s: str, k: int) > str:
# Continue the rounds until the length of s is less than or equal to k
while len(s) > k:
groups = []
# Divide s into consecutive groups of size k
for i in range(0, len(s), k):
group = s[i:i+k]
# Calculate the digit sum of the current group
group_sum = 0
for digit in group:
group_sum += int(digit)
# Append the digit sum to the groups
groups.append(str(group_sum))
# Merge consecutive groups together to form a new string
new_s = ""
for group in groups:
new_s += group
s = new_s
return s

Summary of how the code works:
 Divide the String: We start by dividing the string into groups of size
k
.  Sum the Digits: For each group, we sum the digits.
 Merge the Groups: We concatenate the sums to form a new string.
 Repeat the Rounds: We repeat the above steps until the length of
s
is less than or equal to k
.  Return Result: We return the resultant string.
This code ensures that the rounds are repeated until the length of the string s
becomes less than or equal to k
, following the problem constraints and requirements.