《The C Programming Language》答案（第三章）

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P1

#include 
   
    int binsearch(int x,int v[],int n){
       int low = 0;    int high = n-1;    int mid;    while(low

P2

void escape(char s[],char t[]){
       int i,j;    for(i=0,j=0;t[i]!='\0';i++){
           switch(t[i]){
               case '\n':                s[j++]='\\';                s[j++]='n';                break;            case '\t':                s[j++]='\\';                s[j++]='t';                break;            case '\v':                s[j++]='\\';                s[j++]='v';                break;            case '\b':                s[j++]='\\';                s[j++]='b';                break;            case '\r':                s[j++]='\\';                s[j++]='r';                break;            case '\f':                s[j++]='\\';                s[j++]='f';                break;            case '\a':                s[j++]='\\';                s[j++]='a';                break;            case '\?':                s[j++]='\\';                s[j++]='\?';                break;            case '\'':                s[j++]='\\';                s[j++]='\'';                break;            case '\"':                s[j++]='\\';                s[j++]='\"';                break;            default:                s[j++]=t[i];                break;        }    }    s[j]='\0';}void unescape(char s[],char t[]){
       int i,j;    for(i=0,j=0;t[i]!='\0';i++){
           if(t[i]=='\\'){
               switch(t[++i]){
                   case 'n':                    s[j++]='\n';                    break;                case 't':                    s[j++]='\t';                    break;                case 'v':                    s[j++]='\v';                    break;                case 'b':                    s[j++]='\b';                    break;                case 'r':                    s[j++]='\r';                    break;                case 'f':                    s[j++]='\f';                    break;                case 'a':                    s[j++]='\a';                    break;                case '\\':                    s[j++]='\\';                    break;                case '\?':                    s[j++]='\?';                    break;                case '\'':                    s[j++]='\'';                    break;                case '\"':                    s[j++]='\"';                    break;                default:                    s[j++]='\\';                    --i;                    break;            }        }else{
               s[j++]=t[i];        }    }    s[j] = '\0';}

P3

//buggy!#include 
   
    #define MAXLINE 1024int getchars(char s[],int lim){
       int c,i,l;    for(i=0,l=0;(c=getchar())!=EOF;i++){
           if(i

P4

#include 
   
    #include 
    
     #define MAXLINE 1024void itoa(int n, char s[]){
       int i, sign, remainder;    sign = n;    i = 0;    do {
           remainder = n % 10;        s[i++] = ((sign < 0) ? -remainder : remainder) + '0';    } while (n /= 10);    if (sign < 0)        s[i++] = '-';    s[i] = '\0';    reverse(s);}void reverse(char s[]){
           int i, j;    int tmp;    for (j = 0; s[j] != '\0'; ++j)        ;    --j;    for (i = 0; i < j; ++i, --j) {
           tmp = s[i];        s[i] = s[j];        s[j] = tmp;    }}int main(){
       char s[MAXLINE];    itoa(INT_MIN,s);    printf("%d ---> %s\n",INT_MIN,s);}

P5

#include 
   
    #include 
    
     #define MAXLINE 1024void reverse(char s[]){
       int i, j;    int tmp;    for (j = 0; s[j] != '\0'; ++j)        ;    --j;    for (i = 0; i < j; ++i, --j) {
           tmp = s[i];        s[i] = s[j];        s[j] = tmp;    }}void itob(int n, char s[], int b){
       int i, sign, remainder;    if (b < 2 || b > 36)        return;    sign = n;    i = 0;    do {
           remainder = n % b;        s[i++] = ((sign < 0) ? -remainder : remainder) + '0';    } while (n /= b);    if (sign < 0)        s[i++] = '-';    s[i] = '\0';    reverse(s);}int main(){
       char s[MAXLINE];    itob(INT_MIN,s,8);    printf("%d ---> %s",INT_MIN,s);}

P6

#include 
   
    #include 
    
     #define MAXLINE 1024void reverse(char s[]){
       int i, j;    int tmp;    for (j = 0; s[j] != '\0'; ++j)        ;    --j;    for (i = 0; i < j; ++i, --j) {
           tmp = s[i];        s[i] = s[j];        s[j] = tmp;    }}void itoa(int n, char s[], int w){
       int i, sign, remainder, k, j;    sign = n;    i = 0;    do {
           remainder = n % 10;        s[i++] = ((sign < 0) ? -remainder : remainder) + '0';    } while (n /= 10);    if (sign < 0)        s[i++] = '-';    while (i < w)        s[i++] = ' ';    s[i] = '\0';    reverse(s);}int main(){
       char s[MAXLINE];    int width = 14;    itoa(INT_MIN,s,width);    printf("%12d ---> %s\n",INT_MIN,s);}