Reverse Words in a String III Java Solution - The Coding Shala

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Reverse Words in a String III

Problem:

Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.

Example 1:

Input: "Let's take LeetCode contest"

Output: "s'teL ekat edoCteeL tsetnoc"

Note: In the string, each word is separated by a single space and there will not be any extra space in the string.

Reverse Words in a String III Java Solution

Approach 1:

Using StringBuilder and reverse we can do it.

Java 

class Solution {
    public String reverseWords(String s) {
        s = s.trim();
        int len = s.length()-1;
        StringBuilder ans = new StringBuilder();
        StringBuilder tmp = new StringBuilder();
        int i = 0;
        while(i<=len){
            if(s.charAt(i)==' '){
                tmp.reverse();
                ans.append(tmp).append(" ");
                tmp=new StringBuilder();
                while(i<=len && s.charAt(i)==' ') i++;
            }else{
                tmp.append(s.charAt(i)); 
                i++;
            }
        }
        tmp.reverse();
        ans.append(tmp);
        return ans.toString();
    }
}

Approach 2:

We can convert String into a char array and then reverse the char till space.

Java 

class Solution {
    public String reverseWords(String s) {
        s = s.trim();
        char[] ans = s.toCharArray();
        int i = 0, j = s.length(),tmp=0;
        while(i<j){
            if(ans[i]==' '){
                reverse(ans, tmp, i-1);
                tmp = i+1;
            }
            i++;
        }
        reverse(ans, tmp, j-1);
        return new String(ans);
    }
    
    public void reverse(char[] ans, int start, int end){
        while(start<end){
           char t = ans[start];
            ans[start] = ans[end];
            ans[end] = t;
            start++;
            end--;
        }
    }
}

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