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Leetcode[151] Reverse Words in a String

12 Nov 2015

###Task1 Given an input string, reverse the string word by word.

For example, Given s = “the sky is blue”, return “blue is sky the”.

###Python ####Three steps

class Solution(object):
    def reverseWords(self, s):
        """
        :type s: str
        :rtype: str
        """
        if not s or len(s) == 0:
            return s
        li = s.split()
        rev = []
        for ori in li:
            rev.append(ori[::-1])
        return ' '.join(rev)[::-1]

####Python

class Solution(object):
    def reverseWords(self, s):
        """
        :type s: str
        :rtype: str
        """
        if not s or len(s) == 0:
            return s
        return ' '.join(s.split()[::-1])

####By Char

class Solution(object):
    def reverseWords(self, s):
        """
        :type s: str
        :rtype: str
        """
        res = ''
        word = ''
        for ch in s:
            if ch != ' ':
                word += ch
            elif len(word) > 0:
                if len(res) != 0:
                    res = ' ' + res
                res = word + res
                word = ''
        if len(word) > 0:
            if len(res) != 0:
                res = ' ' + res
            res = word + res
        return res

###Java

public class Solution {
    public String reverseWords(String s) {
        if (s == null || s.length() == 0) {
        	return "";
        }
        s = s.trim();
        StringBuilder sb = new StringBuilder();
        StringBuilder res = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
        	if (s.charAt(i) == ' ') {
        		if (sb.length() == 0) {
        			continue;
        		} else {
	        		res.append(sb.reverse());
	        		if (i != s.length() - 1) {
	        			res.append(" ");
	        		}
	        		sb.delete(0, sb.length());        			
        		}
        	} else {
        		sb.append(s.charAt(i));
        	}
        }

        res.append(sb.reverse());

        return res.reverse().toString();
    }

    public static void main(String[] args) {
    	Solution sol = new Solution();
    	System.out.println(sol.reverseWords(" 1 "));
    }
}

####By split

public class Solution {
    public String reverseWords(String s) {
        if (s == null || s.length() == 0) {
        	return "";
        }

        String[] arr = s.split(" ");
        StringBuilder sb = new StringBuilder();

        for (int i = arr.length - 1; i >= 0; i--) {
            if (!arr[i].equals("")) {
                sb.append(arr[i]).append(" ");
            }
        }

        //remember to remove the last " "
        return sb.length() == 0 ? "" : sb.substring(0, sb.length() - 1);
    }

    public static void main(String[] args) {
    	Solution sol = new Solution();
    	System.out.println(sol.reverseWords(" 1 "));
    }
}

###Points

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