151. Reverse-Words-in-a-String

difficulty: Medium

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Given an input string, reverse the string word by word.

Example 1:

Input: "the sky is blue"
Output: "blue is sky the"

Example 2:

Input: "  hello world!  "
Output: "world! hello"
Explanation: Your reversed string should not contain leading or trailing spaces.

Example 3:

Input: "a good   example"
Output: "example good a"
Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.

Note:

• A word is defined as a sequence of non-space characters.

• Input string may contain leading or trailing spaces. However, your reversed string should not contain leading or trailing spaces.

• You need to reduce multiple spaces between two words to a single space in the reversed string.

Follow up:

For C programmers, try to solve it in-place in O(1) extra space.

Method One

class Solution {
    public String reverseWords(String s) {
        String[] strings = s.trim().split(" ");
        StringBuilder sb = new StringBuilder();
        for(int i = strings.length - 1; i >= 0; i-- ) {
            if(strings[i].compareTo("") == 0 ) {
                continue;
            }
            sb.append( strings[i] );
            sb.append(" ");
        }
        return sb.toString().trim();
    }
}
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