shaobin0604

/*
 * Exercise 2-4. Write an alternative version of squeeze(s1,s2) that deletes 
 * each character in s1 that matches any character in the string s2.  
 */
#include <stdio.h>
#include <stdlib.h>

void squeeze(char s1[], const char s2[]);
int indexof(const char s[], char c);

shaobin0604

/*
 * Exercise 2-5. Write the function any(s1,s2), which returns the first 
 * location in a string s1 where any character from the string s2 occurs, 
 * or -1 if s1 contains no characters from s2. (The standard library 
 * function  strpbrk does the same job but returns a pointer to the location.) 
 */
#include <stdio.h>

int any(const char s1[], const char s2[]);

shaobin0604

/* 
 * Exercise 2-6. Write a function setbits(x,p,n,y) that returns x with the n bits
 * that begin at position p set to the rightmost n bits of y, leaving the other 
 * bits unchanged.
 */
#include <stdio.h>

unsigned int setbits(unsigned int x, int p, int n, unsigned int y);

unsigned int setbits(unsigned int x, int p, int n, unsigned int y) {

shaobin0604

/*
 * Exercise 2-7. Write a function  invert(x,p,n) that returns x with the n 
 * bits that begin at position p inverted (i.e., 1 changed into 0 and vice 
 * versa), leaving the others unchanged.  
 */
#include <stdio.h>

unsigned int invert(unsigned int x, int p, int n);

unsigned int invert(unsigned int x, int p, int n) {

shaobin0604

/*
 * Exercise 2-9. In a two's complement number system, x &= (x-1) deletes the
 * right most 1-bit in x. Explain why. Use this observation to write a faster 
 * version of bitcount. 
 */
#include <stdio.h>

int bitcount(unsigned int x);

int bitcount(unsigned int x) {

shaobin0604

/*
 * Exercise 2-8. Write a function rightrot(x,n) that returns the value of the
 * integer x rotated to the right by n positions.
 */
#include <stdio.h>

unsigned int rightrot(unsigned int x, int n);

unsigned int rightrot(unsigned int x, int n) {
	while (n > 0) {

shaobin0604

/*
 * Exercise 3-2. Write a function  escape(s,t) that converts characters like 
 * newline and tab into visible escape sequences like \n and \t as it copies 
 * the string t to s. Use a switch. Write a function for the other direction 
 * as well, converting escape sequences into the real characters.  
 */

#include <stdio.h>
#define MAXLEN 1000
int escape(char s[], const char t[]);

shaobin0604

#include <ctype.h>

/*
 * 将十进制字符串转换为数值。可处理前导的 + 和 - 
 *
 * 如果有空白符，则跳过
 * 如果有符号，则读取符号
 * 取整数部分，并执行转换
 * 当遇到第一个不能转换为数字的字符时，整个处理过程终止
 */

shaobin0604

/*
 * Exercise 3-3. Write a function expand(s1,s2) that expands shorthand 
 * notations like a-z in the string s1 into the equivalent complete list 
 * abc...xyz in s2. Allow for letters of either case and digits, and be 
 * prepared to handle cases like a-b-c and a-z0-9 and -a-z. Arrange that 
 * a leading or trailing - is taken literally.  
 */

#include <stdio.h>

shaobin0604

/*
 * Exercise 3-4. In a two's complement number representation, our version of 
 * itoa does not handle the largest negative number, that is, the value of n 
 * equal to -(2^wordsize - 1). Explain why not. Modify it to print that value 
 * correctly, regardless of the machine on which it runs.  
 */

#include <stdio.h>
#include <limits.h>
#include <string.h>