3-3-1.c

2005软件工程师考试下午编程题源代码

/*中国系统分析员顾问团，http://www.csai.cn*/
/*程序员下午考试指南书籍源码*/

#include <stdio.h>
#include <malloc.h>
#include <conio.h>
#define CR 13
typedef struct node{
char ch;
struct node *forward; 	/* Link to next node. */
struct node *backward;	/* Link to previous node.*/
} CODE;

main(){
char *decode(), old[256];
int strlen() , key, num=0;
printf("\nPlease input the telegraph: \n");
while ( num < 255 && ( old[num++] = getch()) != CR );
old [ (num==255)?num:num-1 ] = '\0';
do {
printf( "\nPlease input Key=?( Key>1 ):" );
scanf("%d",&key);
} while ( key <= 1 );
printf( "\nThe decode of telegraph:'%s' is:\n'%s'\n",old,decode( old,key ) );
}

char *decode(char *old, int key){
char *new; int length,count,i;
CODE *loop,*p;
length = strlen(old);
loop=( CODE * ) malloc( length*sizeof(CODE) );
for ( i = 1; i < length-1; i++ ){ 
loop[i].forward = &loop[i+1];
loop[i].backward = &loop[i-1];
}
loop[0].backward = &loop[length-1];
loop[0].forward = &loop[1];
loop[length-1].forward = loop;
loop[length-1].backward = &loop[length-2];
for ( p = loop,i = 0; i < length; i++ ){
for ( count = 1;count<key;count++ )
p = p->forward ;
p->ch = *old++;
p->backward->forward = p->forward ;
p->forward->backward = p->backward ;
p = p->forward;
}
new = ( char *)malloc( ( length+1 ) *sizeof(char) );
for ( i = 0; i < length; i++ ) new[i] = loop[i].ch;
new[length]='\0';
return (new);
}

int strlen(char *s){
int len = 0;
while ( *s++ != '\0' )  len++;
return( len );
}