sicily 1323. Switch text

Description
The program must switch the text lines in a backward order and split them by the middle, processing the input lines in pairs. If an empty or blank line is found, it is considered as a line but it is not printed out to the output.

Input
The input will be a text file with text lines.

Output
Standard output with the switched and splitted lines.

题目理解有点困难。拿样例输入的两句做题解，就是这样的

This lines must be printed backwards and splitted in the middle.
And each line too!
↓两行交换
And each line too!
This lines must be printed backwards and splitted in the middle.
↓字母倒转
!oot enil hcae dnA
elddim eht ni dettilps dna sdrawkcab detnirp eb tsum senil sihT.
↓分成两半
!oot enil/*分开*/ hcae dnA
elddim eht ni dettilps dna sdra/*分开*/wkcab detnirp eb tsum senil sihT.
↓两半调转顺序，输出
 hcae dnA!oot enil
wkcab detnirp eb tsum senil sihT.elddim eht ni dettilps dna sdra

注意奇数长度的字符串的分割方法，设长度为2k+1，输出的第一半就是k+1~1，第二半是2k+1~k+2

虽然题目没有讲，但是是用EOF结束输出的。还有就是空行的判断方法要留点心，因为题目里说空行有两种，一是全空格，一是连空格都没有，直接回车。

有两种办法做，可以开数组，先倒转，然后将两半错开填进去，比较好理解，也比较啰嗦

#include<stdio.h>
#include<string.h>
#define SIZE 10001
int isEmpty ( char str[] );
void switchAndSplit( char str[] );
void printString( char str[], int len );
int main()
{
    char str1[SIZE] = {0};
    char str2[SIZE] = {0};
    while ( gets(str1) )
    {
        gets(str2);
        switchAndSplit(str2);
        switchAndSplit(str1);
    }
    return 0;
}

int isEmpty ( char str[] )
{
    int len, i;
    
    len = strlen(str);
    
    for ( i = 0; i < len; i++ )
    {
        if ( str[i] != ' ' )
        {
            return 0;
        }
    }
    
    return 1;
}

void switchAndSplit( char str[] )
{
    int len;
    int i, j;
    char temp[SIZE] = {0};
    char part1[SIZE] = {0};
    char part2[SIZE] = {0};
    char switched[SIZE] = {0};
    char splited[SIZE] = {0};
    
    len = strlen(str);
    
    if ( isEmpty(str) == 0 )
    {
        for ( i = 0; i < len; i++ )
        {
            switched[i] = str[len - i - 1];
        } 
        
        j = 0;
        
        for ( i = len / 2; i < len; i++ )
        {
            splited[j] = switched[i];
            j++;
        }
        
        for ( i = 0; i < len / 2; i++ )
        {
            splited[j] = switched[i];
            j++;
        }
        
        printString( splited, j );
    }
    
}

void printString( char str[], int len )
{
    int i;
    
    for ( i = 0; i < len; i++ )
    {
        printf( "%c", str[i] ); 
    }
    
    printf("\n");
}

第二种是用指针做，只是改变输出字符的顺序，比较简洁，但是分割点的设置比较烦（也可能只是我设的比较烦……）

#include<stdio.h>
#include<string.h>
#define SIZE 10001
int isEmpty ( char str[] );
void switchAndSplit( char str[] );
void printString( char str[], int len );
int main()
{
    char str1[SIZE] = {0};
    char str2[SIZE] = {0};
    while ( gets(str1) )
    {
        gets(str2);
        switchAndSplit(str2);
        switchAndSplit(str1);
    }
    return 0;
}

int isEmpty ( char str[] )
{
    int len, i;
    
    len = strlen(str);
    
    for ( i = 0; i < len; i++ )
    {
        if ( str[i] != ' ' )
        {
            return 0;
        }
    }
    
    return 1;
}

void switchAndSplit( char str[] )
{
    int len;
    int i, j;
    char temp[SIZE] = {0};
    char part1[SIZE] = {0};
    char part2[SIZE] = {0};
    char switched[SIZE] = {0};
    char splited[SIZE] = {0};
    
    len = strlen(str);
    
    if ( isEmpty(str) == 0 )
    {
        for ( i = 0; i < len; i++ )
        {
            switched[i] = str[len - i - 1];
        } 
        
        j = 0;
        
        for ( i = len / 2; i < len; i++ )
        {
            splited[j] = switched[i];
            j++;
        }
        
        for ( i = 0; i < len / 2; i++ )
        {
            splited[j] = switched[i];
            j++;
        }
        
        printString( splited, j );
    }
    
}

void printString( char str[], int len )
{
    int i;
    
    for ( i = 0; i < len; i++ )
    {
        printf( "%c", str[i] ); 
    }
    
    printf("\n");
}