[Leetcode] 482. License Key Formatting 解题报告

题目：

You are given a license key represented as a string S which consists only alphanumeric character and dashes. The string is separated into N+1 groups by N dashes.

Given a number K, we would want to reformat the strings 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 all lowercase letters should be converted to uppercase.

Given a non-empty string S and a number K, format the string according to the rules described above.

Example 1:

Input: S = "5F3Z-2e-9-w", K = 4

Output: "5F3Z-2E9W"

Explanation: The string S has been split into two parts, each part has 4 characters.
Note that the two extra dashes are not needed and can be removed.

Example 2:

Input: S = "2-5g-3-J", K = 2

Output: "2-5G-3J"

Explanation: The string S has been split into three parts, each part has 2 characters except the first part as it could be shorter as mentioned above.

Note:

1. The length of string S will not exceed 12,000, and K is a positive integer.
2. String S consists only of alphanumerical characters (a-z and/or A-Z and/or 0-9) and dashes(-).
3. String S is non-empty.

思路：

练手题目，注意实现细节即可。

代码：

class Solution {
public:
    string licenseKeyFormatting(string S, int K) {
        string mid_ret, ret;
        for (auto c : S) {
            if (c != '-') {
                mid_ret += toupper(c);
            }
        }
        int remain = mid_ret.length() % K, start = 0;
        if (remain != 0) {
            ret += mid_ret.substr(0, remain);
            ret += '-';
            start = remain;
        }
        while (start != mid_ret.length()) {
            ret += mid_ret.substr(start, K);
            ret += '-';
            start += K;
        }
        ret.pop_back();
        return ret;
    }
};