#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;

void swap()
{
        string str;
        int a[50],b=0;
        getline(cin,str);

        int leng=str.length();
        for(int j = 0; j < leng; j++)
        {
            if(str[j] == ' ')
            {
                b++;
                a[b] = j;
            }
        }
        a[0] = -1;
        string str1[b+1];
        int record[b+1];

        for(int k = 0; k < b; k++)
        {
            int n = 0;
            for(int j = a[k]+1;j < a[k+1]; j++)
            {
                str1[k][n] = str[j];
                record[k+1] = n;
                n++;
            }
        }
        int m = 0;
        for(int j = a[b]+1; j < leng; j++)
        {
            str1[b][m] = str[j];
            record[b+1] = m;
            m++;
        }
        record[0] = 0;
        for(int j = 0; j < b+1; j++)
        {
            for(int k = record[j+1]; k >= 0; k--)
            {
                cout << str1[j][k];
            }
            cout << " ";
        }
        cout << endl;

}
int main()
{
    int times,leng;
    cin >> times;
    cin.get();
    for(int i = 0; i < times; i++)
    {
        swap();
    }


    return 0;
}
这个是错的，我后来换了种思路做了如下。
#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;

void swap()
{
        string str;
        int a[50],b=0;
        getline(cin,str);

        int leng=str.length();
        for(int j = 0; j < leng; j++)
        {
            if(str[j] == ' ')
            {
                b++;
                a[b] = j;
            }
        }
        a[0] = -1;
        a[b+1] = leng;
        string st[b+1];
        char c;

        for(int j = 0; j < b+1; j++)
        {
            if(j ==  b)
            {
            st[j] = str.substr(a[j]+1,a[j+1]-a[j]-1);

            }
            if(j != b)
            {
            st[j] = str.substr(a[j]+1,a[j+1]-a[j]-1);

            }
        }
        for(int j = 0; j < b+1; j++)
        {
            for(int k = 0; k < (a[j]+1,a[j+1]-a[j])/2; k++){
            c = st[j][k];
            st[j][k]= st[j][a[j]+1,a[j+1]-a[j]-2-k];
            st[j][a[j]+1,a[j+1]-a[j]-2-k] = c;
            }
            if(j == b)
            cout << st[j]<<endl;
            if(j != b)
            cout << st[j] << " " ;
        }


}
int main()
{
    int times,leng;
    cin >> times;
    cin.get();
    for(int i = 0; i < times; i++)
    {
        swap();
    }


    return 0;
}
我想知道为什么第一种方案 运行一次会运行不下去。

题目是

For each list of words, output a line with each word reversed without changing the order of the words.


Input

You will be given a number of test cases. The first line contains a positive integer indicating the number of cases to follow. Each case is given on a line containing a list of words separated by one space, and each word contains only uppercase and lowercase letters.


Output

For each test case, print the output on one line.


Sample Input

3
I am happy today
To be or not to be
I want to win the practice contest


Sample Output

I ma yppah yadot
oT eb ro ton ot eb
I tnaw ot niw eht ecitcarp tsetnoc

int j定义了这么多次，你编译过了没?
 string st[b+1];这里的定义也过不去。
不过代码的功能好像差不多了，但是有问题。输出很不正常。

编译过了
定义也过了
输出是不正常...

int j没有定义多次，这是你错，因为你用的是不符号C++标准的编译器
string st[b+1]属于C99的变长数组但C++不允许，这是楼主错，因为楼主使用了非标准的编译器扩展

那应该如何改进

一个多小时才写好 太菜了  
楼主一起学习哈

主要是在对string的输入和输出处理上耽搁时间了

#include<iostream>
#include <string>
using namespace std;
int main()
{
    int n;
    cin>>n;
    while ( n )
    {
        string str;
        fflush(stdin);
        getline(cin,str);//?这里无法读取数据
        string::size_type index;
        int end=0;
        for (index=0; index!=str.size(); index++)
        {
            if (str[index] == ' ')
            {
                int begin=index-1;
                for (; begin>=end; begin--)//使用size_type类型出错
                {
                    cout<<str[begin];
                }
                cout<<" ";
                end=index+1;
            }
            if (index == str.size()-1)//最后一个单词
            {
                int begin=index;
                for (; begin>=end; begin--)
                {
                    cout<<str[begin];
                }
                cout<<endl;
            }
            
        }
        --n;
    }
    return 0;
}

  楼上正解！