Reverse Words in a String II

最新推荐文章于 2019-11-25 21:02:45 发布

flyatcmu

最新推荐文章于 2019-11-25 21:02:45 发布

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分类专栏： String

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本文介绍了一种高效的字符串反转算法，该算法能够逐词反转输入的字符串，且操作在原字符串上进行，无需额外分配空间。通过两次反转操作实现，首先整体反转整个字符串，然后逐个反转每个单词。

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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?

思路：就是先整体reverse，然后再每个局部reverse，记得最后while跳出来之后，最后一个单词也要reverse一下；

public class Solution {
    public void reverseWords(char[] s) {
        if(s == null || s.length == 0) return;
        reverse(s, 0, s.length-1);
        int i=0; int j=0;
        while(j<s.length){
            while(j<s.length && s[j] != ' '){
                j++;
            }
            if(j>=s.length) break;
            reverse(s, i, j-1);
            i=j+1;
            j++;
        }
        reverse(s, i, j-1);
    }
    
    public void reverse(char[] s, int i, int j) {
        while(i<j) {
            char temp = s[i];
            s[i] = s[j];
            s[j] = temp;
            i++;
            j--;
        }
    }
}