482. License Key Formatting

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.

非常好奇我把类似这样的ans=ans+tmp[index]  改成ans+=tmp[index]就能通过，而前者却是Memory Limit Exceeded

class Solution {
public:
    string licenseKeyFormatting(string S, int K) {
        int i,j,index;
        string tmp="",ans="";
        for(i=0;i<S.length();i++){
            if(S[i]!='-'){
                tmp+=toupper(S[i]);
            }
        }
        for(index=0;index<tmp.length()%K;index++){//前面不足K个
            ans+=tmp[index];
        }
        if(index!=0&&tmp.length()-tmp.length()%K>0){//前面不足K个并且后面还有，需要 -
            ans+='-';
        }
        for(i=0;i<tmp.length()-tmp.length()%K;i++){           
            if(i>0&&i%K==0){
               ans+='-'; 
            }
            ans+=tmp[index++];
        }
        return ans;
    }
};

标签：tmp,index,string,License,Formatting,characters,ans,482,dashes
来源： https://blog.csdn.net/lyw_321/article/details/97959146