翻转单词顺序 Reverse Words in a String

问题：Given an input string, reverse the string word by word. For example,

Given s = "the sky is blue",
return "blue is sky the".

思路：两轮翻转。第一次整个串彻底反转，第二次逐个单词自身翻转。

输入用例：

输入数据的细节特别重要。开头有空格、结尾有空格、多个空格并列。

class Solution {public:    void reverseWords(string &s) {        int n = s.size();        if(n == 0)            return;                string A = "";        int idx, left, right;        right = n-1;        while(right >= 0 && s[right] == ' ') //去除右侧空格            right--;        if(right < 0)        {            s = "";            return;        }        idx = 0;        while(idx <= right && s[idx] == ' ') //去除左侧空格            idx++;        while(idx <= right)        {            if(s[idx] != ' ' || s[idx-1] != ' ') //拷贝字符和单空格                A += s[idx];           idx++;        }                n = A.size();        reverse(A, 0, n-1);                idx = 0;        while(idx < n)        {            left = idx;            while(idx < n && A[idx] != ' ')                idx++;            right = idx-1;            reverse(A, left, right);            idx++; //跳过空格        }                s = A;    }        void reverse(string &s, int left, int right)    {        while(left < right)            swap(s[left++], s[right--]);    }};

下面是jobduOJ的程序，注意：如果要键盘录入一个字符串，其中含有空格，那么最好用gets(str)。

# include<stdio.h># include<string.h># include<malloc.h> int reverse(char *str, int left, int right) //添加两个参数来控制翻转位置{if(left<0 || left>right || right>strlen(str)-1) //合法性检查return 0;char tmp;while(left<right) //左右游标控制{tmp = str[left];str[left] = str[right];str[right] = tmp;left++;right--;}return 1; //学会返回函数执行状态}void re_order(char *str){int len = strlen(str);int i=0,j=0;while(j<len){while(str[j] != ' ' && str[j] !='\0') //操作检查和合法性检查{j++;}reverse(str, i, j-1);j++;i = j;}}int main(){char a[50000];while(gets(a)){reverse(a, 0, strlen(a)-1);re_order(a);printf("%s\n",a);}return 1;}