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7. < tag string and API trade-offs> supplement: Sword finger offer 05. replace spaces

2022-07-28 05:12:00 【Caicai's big data development path】

lt. The finger of the sword Offer 05. Replace blank space

[ Case needs ]

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[ Train of thought analysis 1 , Use API]

Use StringBuilder, Continue to traverse the original string , stay sb.append When spaces are encountered in the process , Replace with %20 that will do ;

[ Code implementation ]

// Use a new object , Copy  str, The process of copying is judged , If it is a space, replace , Otherwise, copy directly , Similar to array copy 
public static String replaceSpace(StringBuffer str) {
    
        if (str == null) {
    
            return null;
        }
		// choose  StringBuilder  Single thread use , Faster , Choose or not 
        StringBuilder sb = new StringBuilder();
		// Use  sb  Copy one by one  str , If you encounter a space, replace , Otherwise, copy directly 
        for (int i = 0; i < str.length(); i++) {
    
		//str.charAt(i)  by  char  type , Turn it into a need for comparison  " "  Same string type 
        //if (" ".equals(String.valueOf(str.charAt(i)))){
    
            if (s.charAt(i) == ' ') {
    
                sb.append("%20");
            } else {
    
                sb.append(str.charAt(i));
            }
        }
        return sb.toString();
    }

perhaps

class Solution {
    
    public String replaceSpace(String s) {
    
        //
        StringBuilder sb = new StringBuilder();

        for(Character c : s.toCharArray()){
    
            if(c == ' '){
    
                sb.append("%20");
                continue;
            }
            sb.append(c);
        }

        return sb.toString();
    }
}

[ Train of thought analysis II , Don't use API]

Create a character array , Then traverse String Each of them char character ,
Note the length of this character array -> Because a space becomes three characters (%20), So the total length The maximum is 3 Times the original string length ( Of course, if there are other elements besides spaces , So it's unlikely to run out )

[ Code implementation ]

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