Sword finger offer 58 - I. flip word order

Title Description

Enter an English sentence , Turn over the order of the words in the sentence , But the order of the characters in the word is the same . For the sake of simplicity , Punctuation is treated like ordinary letters . For example, input string "I am a student. “, The output "student. a am I”.

Problem analysis

This problem uses the method of double pointers to traverse
s.trim() Method remove the space bar , Give Way i,j Traverse from the tail when i When traversing the space , Use substring Intercept , Cut out the words and put them in res newly build StringBuilder Back , End use tostring Convert to string .

Code instance

/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */
class Solution {
    
    public String reverseWords(String s) {
    
        public String reverseWords(String s) {
    
        s = s.trim();
        int i = s.length() - 1;
        int j = i;
        StringBuilder res = new StringBuilder();
        while(i >= 0){
    
            while(i >= 0 && s.charAt(i) != ' '){
    
                i--;
            }
            res.append(s.substring(i + 1,j + 1) + ' ');
            while(i >= 0 && s.charAt(i) == ' '){
    
                i--;
            }
            j = i;
        }
        return res.toString().trim();
    }
    }
}