题目:
Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.
The input string does not contain leading or trailing spaces and the words are always separated by a single space.
For example,
Given s = "the sky is blue",
return "blue is sky the".
Could you do it in-place without allocating extra space?
分析:
这题应用的原理是两次求逆等于原String的原则, 第一次将整体String全部求逆, 然后利用单词之间的空格, 再分开求逆,最后实现将整个sentence单词完全倒序的结果. 比较巧妙
代码:
public class Solution {
public void reverseWords(char[] s) {
reverse(s, 0, s.length);
for (int i = 0, j = 0; j <= s.length; j++){
if (j == s.length || s[j] == ' ') {
reverse(s, i , j);
i = j + 1;
}
}
}
private void reverse(char[] s, int start, int end) {
for (int i = 0; i < (end - start) / 2; i++) {
char temp = s[start + i];
s[start + i] = s[end - i - 1];
s[end - i - 1] = temp;
}
}
}