- Reverse Words in a String II
Given an input character array, reverse the array word by word. A word is defined as a sequence of non-space characters.
The input character array does not contain leading or trailing spaces and the words are always separated by a single space.
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Problem Correction
Example
Example1
代码语言：javascript复制Input: s = "the sky is blue"
Output: "blue is sky the" Example2
代码语言：javascript复制Input: "a b c"
Output: "c b a" Challenge
Could you do it in-place without allocating extra space?
思路：
因为题目要求只能在原数组操作，不能申请额外的空间，并且字母之间只有一个空格，所以使用翻转两次的方式，第一次翻转整个字符串，第二次翻转单个单词。
代码：
java：
代码语言：javascript复制public class Solution {
/**
* @param str: a string
* @return: return a string
*/
public char[] reverseWords(char[] str) {
if (str == null || str.length == 0) return new char[]{};
int len = str.length;
// 1. reverse whole string
reverse(str, 0, len - 1);
// 2. reverse single word
int start = 0, i = 0;
for (;i < len; i ) {
if (str[i] == ' ') {
reverse(str, start, i - 1);
start = i 1;
}
}
reverse(str,start, i-1);
return str;
}
private void reverse(char[] s, int i, int j) {
while( i < j) {
char temp = s[i];
s[i ] = s[j];
s[j--] = temp;
}
}
}
