[LC] 151. Reverse Words in a String

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.

Solution 1:

class Solution {

    public String reverseWords(String s) {

        if (s == null || s.length() == 0) {

            return "";

        }

        char[] charArr = s.toCharArray();

        swap(charArr, 0, s.length() - 1);

        int i = 0, start = 0;

        while (i < s.length()) {

            if (i == 0 || charArr[i - 1] == ' ') {

                start = i;

            }

            if (i == charArr.length - 1 || charArr[i + 1] == ' ') {

                swap(charArr, start, i);

            }

            i += 1;

        }

        // need to trim space inside

        int slow = 0;

        for (int j = 0; j < charArr.length; j++) {

            if (charArr[j] == ' ' && (j == 0 || charArr[j - 1] == ' ')) {

                continue;

            }

            charArr[slow++] = charArr[j];

        }

        return new String(charArr, 0, slow).trim();

    }

    private void swap(char[] charArr, int i, int j) {

        while (i < j) {

            char tmp = charArr[i];

            charArr[i] = charArr[j];

            charArr[j] = tmp;

            i += 1;

            j -= 1;

        }

    }

}

Solution 2:

class Solution {

    public String reverseWords(String s) {

        if (s == null || s.length() == 0) {

            return "";

        }

        String[] strArr = s.split("\\s+");

        StringBuilder sb = new StringBuilder();

        for (int i = strArr.length - 1; i >= 0; i--) {

            sb.append(strArr[i] + " ");

        }

        return sb.toString().trim();

    }

}

巴特西

[LC] 151. Reverse Words in a String

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