Sword finger offer 05.58 Ⅱ string

Topic 1 ：

The finger of the sword Offer 05. Replace blank space https://leetcode-cn.com/problems/ti-huan-kong-ge-lcof/

  Ideas : Traversal character array , Replace . Seem to use stringbuilder faster

Code :

// use string
class Solution {
    public String replaceSpace(String s) {
        String res = "";
        for(Character c : s.toCharArray())
        {
            if(c == ' ') 
                res+="%20";
            else 
                res+=c;
        }
        return res;
    }
}

// use stringBulider
class Solution {
    public String replaceSpace(String s) {
        StringBuilder res = new StringBuilder();
        for(Character c : s.toCharArray())
        {
            if(c == ' ') 
                res.append("%20");
            else 
                res.append(c);
        }
        return res.toString();
    }
}

result :

Topic two :

idea : Obtain substring parallel splicing in two times

Code :

class Solution {
    public String reverseLeftWords(String s, int n) {
        String res="";
        res+=s.substring(n,s.length());
        res+=s.substring(0,n);
        return res;
    }
}

  result :

Idea 2 : Out of commission substring when , It can be added to the new string twice .

Using the remainder method can simplify the code

Reference resources : author ：jyd
link ：https://leetcode-cn.com/problems/zuo-xuan-zhuan-zi-fu-chuan-lcof/solution/mian-shi-ti-58-ii-zuo-xuan-zhuan-zi-fu-chuan-qie-p/

Code :

class Solution {
    public String reverseLeftWords(String s, int n) {
        StringBuilder res = new StringBuilder();
        for(int i = n; i < n + s.length(); i++)
            res.append(s.charAt(i % s.length()));
        return res.toString();
    }
}

  result :