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Given an input string, reverse the string word by word.
For example,
Given s = "the sky is blue",
return "blue is sky the".
For C programmers: Try to solve it in-place in O(1) space.
Clarification:
思路：翻转的思路是很清楚的，就是卡在空格上了。结果专门先循环一遍来去掉空格。
注意，必须改变指针中所对应的值才能改变字符串。
void reverse(char * s, char * e) { while(s < e) { char tmp = *s; *s = *e; *e = tmp; s++; e--; } } void reverseWords(char *s) { //先专门处理空格 char * p = s; char * snew = s; while(*p != ‘\0‘) { if(*p != ‘ ‘) *snew++ = *p++; else if(snew == s) p++; //开始处遇到空格 else if(*(snew - 1) == ‘ ‘) p++; //已经有了一个空格 else *snew++ = *p++; } *snew = ‘\0‘; if(*(snew - 1) == ‘ ‘) *(snew - 1) = ‘\0‘; //翻转 char *ss = s; int start = 0, end = 0; while(*ss != ‘\0‘) { while(*ss != ‘ ‘ && *ss != ‘\0‘) { ss++; end++; } reverse(s + start, s + end - 1); if(*ss != ‘\0‘) { ss++; end++; start = end; } } reverse(s, s + end - 1); }
看看大神的：不用先去除空格，而是在遍历的过程中用end来更新字符串，去掉空格。
// reverses the part of an array and returns the input array for convenience public char[] reverse(char[] arr, int i, int j) { while (i < j) { char tmp = arr[i]; arr[i++] = arr[j]; arr[j--] = tmp; } return arr; } public String reverseWords(String s) { // reverse the whole string and convert to char array char[] str = reverse(s.toCharArray(), 0, s.length()-1); int start = 0, end = 0; // start and end positions of a current word for (int i = 0; i < str.length; i++) { if (str[i] != ‘ ‘) { // if the current char is letter str[end++] = str[i]; // just move this letter to the next free pos } else if (i > 0 && str[i-1] != ‘ ‘) { // if the first space after word reverse(str, start, end-1); // reverse the word str[end++] = ‘ ‘; // and put the space after it start = end; // move start position further for the next word } } reverse(str, start, end-1); // reverse the tail word if it‘s there // here‘s an ugly return just because we need to return Java‘s String // also as there could be spaces at the end of original string // we need to consider redundant space we have put there before return new String(str, 0, end > 0 && str[end-1] == ‘ ‘ ? end-1 : end); }
【leetcode】Reverse Words in a String(hard)☆
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原文地址：http://www.cnblogs.com/dplearning/p/4435219.html
