1214. License Key Formatting

描述

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.

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

您在真实的面试中是否遇到过这个题？  是

样例

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.

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.

倒着依次遍历就可以了。

class Solution {
public:
    /**
     * @param S: a string
     * @param K: a integer
     * @return: return a string
     */
    string licenseKeyFormatting(string &S, int K) {
        // write your code here
        string result;
        int tmp=0;
        for(int i=S.length()-1;i>=0;i--){
            if(S[i]=='-') continue;
            if(S[i]-'a'>=0&&S[i]-'a'<26)
                result=(char)('A'+S[i]-'a')+result;
            else result=S[i]+result;
            tmp++;
            if(tmp==K&&i!=0) {
                result='-'+result;
                tmp=0;
            }
        }
        return result;
    }
};