Sword finger offer05 Replace spaces

The finger of the sword Offer05. Replace blank space

Please implement a function , Put the string s Replace each space in with "%20".

Example 1：

 Input ：s = "We are happy."
 Output ："We%20are%20happy."

Limit ：

0 <= s The length of <= 10000

JAVA Code

Tool class methods

Here's a list of , But you can't take advantage of opportunism ~~

class Solution {
    
    public String replaceSpace(String s) {
    
        return s.replace(" ","%20");
    }
}

The official way

By converting a string into a character array , Analyze the string character by character , If it is a space, insert it into the array % 2 0 Three characters , If it is not a space, insert the position character directly into the array .
Be careful ： Not directly arr.toString() To string , It's messy .
new String( Source array , The starting position , Termination position )

class Solution {
    
    public String replaceSpace(String s) {
    
        char[] arr = new char[s.length()*3];
        int index = 0;
        for(int i = 0;i<s.length();i++){
    
            if(s.charAt(i)==' '){
    
                arr[index++] = '%';
                arr[index++] = '2';
                arr[index++] = '0';
            }else{
    
                arr[index++] = s.charAt(i);
            }
        }
        String newStr = new String(arr,0,index);
        return newStr;
    }
}

The idea of solving problems is very important .