License Key Formatting Problem & Solution
You are given a license key represented as a string s that consists of only alphanumeric characters and dashes.
The string is separated into n + 1 groups by n dashes.
You are also given an integer k.
We want to reformat the string s such that each group contains exactly k characters, except for the first group, which could be shorter than k but still must contain at least one character.
Furthermore, there must be a dash inserted between two groups, and you should convert all lowercase letters to uppercase.
Return the reformatted license key.
See the license key formatting problem on LeetCode.
C++ Solution
#pragma GCC optimize("Ofast")
#pragma GCC optimization("unroll-loops")
static const int _=[](){ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();
class Solution {
public:
string licenseKeyFormatting(string s, int k) {
int len = 0;
for (int i = 0; i < s.size(); ++i) {
len += s[i] != '-' ? 1 : 0;
}
// Takes care of the case when `s` is made up of only `-`.
if (len == 0) {
return "";
}
string result(len + len / k + (len % k == 0 ? -1 : 0), '-');
int j = result.size() - 1;
int jj = 0;
for (int i = s.size() - 1; i >= 0; --i) {
if (s[i] == '-') {
continue;
}
// Keeps track of how many non `-` characters have been inserted.
++jj;
result[j--] = toupper(s[i]);
if (j > 0 && jj % k == 0) {
--j;
}
}
return result;
}
};