selsolutionsc5.txt

primer c 5th edition 一书详细叙述了c语言的概念和知识。包括17章内容

{
  int r;

  r = x % base;
  if (x >= 2)
     to_base_n(x / base, base);
  putchar('0' + r);
  return;
}

Chapter 10

PE 10-1

/* Programming Exercise 10-1 */
#include <stdio.h>
#define MONTHS 12    /* number of months in a year */
#define YRS   5      /* number of years of data    */
int main(void)
{
 /* initializing rainfall data for 1990 - 1994 */
 const float rain[YRS][MONTHS] = {
 {10.2, 8.1, 6.8, 4.2, 2.1, 1.8, 0.2, 0.3, 1.1, 2.3, 6.1, 7.4},
 {9.2, 9.8, 4.4, 3.3, 2.2, 0.8, 0.4, 0.0, 0.6, 1.7, 4.3, 5.2},
 {6.6, 5.5, 3.8, 2.8, 1.6, 0.2, 0.0, 0.0, 0.0, 1.3, 2.6, 4.2},
 {4.3, 4.3, 4.3, 3.0, 2.0, 1.0, 0.2, 0.2, 0.4, 2.4, 3.5, 6.6},
 {8.5, 8.2, 1.2, 1.6, 2.4, 0.0, 5.2, 0.9, 0.3, 0.9, 1.4, 7.2}
 };
 int year, month;
 float subtot, total;

 printf(" YEAR    RAINFALL  (inches)\n");
 for (year = 0, total = 0; year < YRS; year++)
 {             /* for each year, sum rainfall for each month */
    for (month = 0, subtot = 0; month < MONTHS; month++)
       subtot += *(*(rain + year) + month);
    printf("%5d %15.1f\n", 1990 + year, subtot);
    total += subtot;                  /* total for all years */
 }
 printf("\nThe yearly average is %.1f inches.\n\n", total/YRS);
 printf("MONTHLY AVERAGES:\n\n");
 printf(" Jan  Feb  Mar  Apr  May  Jun  Jul  Aug  Sep  Oct ");
 printf(" Nov  Dec\n");

 for (month = 0; month < MONTHS; month++)
 {               /* for each month, sum rainfall over years */
    for (year = 0, subtot =0; year < YRS; year++)
       subtot += *(*(rain + year) + month);
    printf("%4.1f ", subtot/YRS);
 }
 printf("\n");
 return 0;
}

PE 10-3

/* Programming Exercise 10-3 */
#include <stdio.h>
#define LEN 10 

int max_arr(const int ar[], int n);
void show_arr(const int ar[], int n);

int main(void)
{
    int orig[LEN] = {1,2,3,4,12,6,7,8,9,10};
    int max;
    
    show_arr(orig, LEN);
    max = max_arr(orig, LEN);
    printf("%d = largest value\n", max);
    
    return 0;
}

int max_arr(const int ar[], int n)
{
    int i;
    int max = ar[0];
/* don't use 0 as initial max value -- fails if all array values are neg */
    
    for (i = 1; i < n; i++)
        if (max < ar[i])
            max = ar[i];
    return max;
}

void show_arr(const int ar[], int n)
{
    int i;
    
    for (i = 0; i < n; i++)
        printf("%d ", ar[i]);
    putchar('\n');
}


PE 10-5

/* Programming Exercise 10-5 */
#include <stdio.h>
#define LEN 10 

float max_diff(const float ar[], int n);
void show_arr(const float ar[], int n);

int main(void)
{
    float orig[LEN] = {1.1,2,3,4,12,6,7,8,9,10};
    float max;
    
    show_arr(orig, LEN);
    max = max_diff(orig, LEN);
    printf("%g = maximum difference\n", max);
    
    return 0;
}

float max_diff(const float ar[], int n)
{
    int i;
    float max = ar[0];
    float min = ar[0];
    
    for (i = 1; i < n; i++)
    {
        if (max < ar[i])
            max = ar[i];
        else if (min > ar[i])  
            min = ar[i];
    }
    return max - min;
}

void show_arr(const float ar[], int n)
{
    int i;
    
    for (i = 0; i < n; i++)
        printf("%g ", ar[i]);
    putchar('\n');
}


PE 10-7

/* Programming Exercise 10-7 */
#include <stdio.h>
#define LEN1 7 
#define LEN2 3

void copy_arr(int ar1[], const int ar2[], int n);
void show_arr(const int ar[], int n);

int main(void)
{
    int orig[LEN1] = {1,2,3,4,5,6,7};
    int copy[LEN2];
    
    show_arr(orig, LEN1);
    copy_arr(copy, orig + 2, LEN2);
    show_arr(copy, LEN2);
        
    return 0;
}

void copy_arr(int ar1[], const int ar2[], int n)
{
    int i;
    
    for (i = 0; i < n; i++)
        ar1[i] = ar2[i];
}

void show_arr(const int ar[], int n)
{
    int i;
    
    for (i = 0; i < n; i++)
        printf("%d ", ar[i]);
    putchar('\n');
}

PE 10-10

/* Programming Exercise 10-10 */
#include <stdio.h>
#define ROWS 3
#define COLS 5 

void times2(int ar[][COLS], int r);
void showarr2(int ar[][COLS], int r);

int main(void)
{
    int stuff[ROWS][COLS] = {    {1,2,3,4,5},
                                {6,7,8,9,10},
                                {11,12,13,14,15}
                            };
    showarr2(stuff, ROWS);
    putchar('\n');
    times2(stuff, ROWS);
    showarr2(stuff, ROWS);
        
    return 0;
}

void times2(int ar[][COLS], int r)
{
    int row, col;
    
    for (row = 0; row < r; row++)
        for (col = 0; col < COLS; col++)
            ar[row][col] *= 2;

}

void showarr2(int ar[][COLS], int r)
{
    int row, col;
    
    for (row = 0; row < r; row++)
    {
        for (col = 0; col < COLS; col++)
            printf("%d ", ar[row][col]);
        putchar('\n');
    }
}

PE 10-13

/* Programming Exercise 10-13 */
#include <stdio.h>
#define ROWS 3
#define COLS 5 

void store(double ar[], int n);
double average2d(int rows, int cols, double ar[rows][cols]);
double max2d(int rows, int cols, double ar[rows][cols]);
void showarr2(int rows, int cols, double ar[rows][cols]);
double average(const double ar[], int n);

int main(void)
{
    double stuff[ROWS][COLS];
    int row;
    
    for (row = 0; row < ROWS; row++)
    {
        printf("Enter %d numbers for row %d\n", COLS, row + 1);
        store(stuff[row], COLS);
    }
    
    printf("array contents:\n");
    showarr2(ROWS, COLS, stuff);
    
    for (row = 0; row < ROWS; row++)
        printf("average value of row %d = %g\n", row + 1, average(stuff[row], COLS));
    printf("average value of all rows = %g\n", average2d(ROWS, COLS, stuff));
    printf("largest value = %g\n", max2d(ROWS, COLS, stuff)); 
    printf("Bye!\n");    
    return 0;
}

void store(double ar[], int n)
{
    int i;
    for (i = 0; i < n; i++)
    {
        printf("Enter value #%d: ", i + 1);
        scanf("%lf", & ar[i]);
    }
}
    

double average2d(int rows, int cols, double ar[rows][cols])
{
    int r, c;
    double sum = 0.0;
    
    for (r = 0; r < rows; r++)
        for (c = 0; c < cols; c++)
            sum += ar[r][c];
    if (rows * cols > 0)
        return sum / (rows * cols);
    else
        return 0.0;
}

double max2d(int rows, int cols, double ar[rows][cols])
{
    int r, c;
    double max = ar[0][0];
    
    for (r = 0; r < rows; r++)
        for (c = 0; c < cols; c++)
            if (max < ar[r][c])
                max = ar[r][c];
    return max;

}

void showarr2(int rows, int cols, double ar[rows][cols])
{
    int row, col;
    
    for (row = 0; row < rows; row++)
    {
        for (col = 0; col < cols; col++)
            printf("%g ", ar[row][col]);
        putchar('\n');
    }
}

double average(const double ar[], int n)
{
    int i;
    double sum = 0.0;
    
    for (i = 0; i < n; i++)
        sum += ar[i];
    if (n > 0)
        return sum / n;
    else
        return 0.0;
}

Chapter 11

PE 11-1

/* Programming Exercise 11-1 */
#include <stdio.h>
#define LEN 10
char * getnchar(char * str, int n);
int main(void)
{
    char input[LEN];
    char *chk;
    
    chk = getnchar(input, LEN - 1);
    if (chk == NULL)
        puts("Input failed.");
    else
        puts(input);
    puts("Done.\n");
    
    return 0;
}

char * getnchar(char * str, int n)
{
    int i;
    int ch;

    for (i = 0; i < n; i++)
    {
        ch = getchar();
        if (ch != EOF)
            str[i] = ch;
        else
            break;
    }
    if (ch == EOF)
        return NULL;
    else
    {
        str[i] = '\0';
        return str;
    }
}

PE 11-3

/* Programming Exercise 11-3 */
#include <stdio.h>
#define LEN 80
char * getword(char * str);
int main(void)
{
    char input[LEN];
    char *chk;
    
    while (getword(input) != NULL)
        puts(input);
    puts("Done.\n");
    
    return 0;
}

#include <ctype.h>
char * getword(char * str)
{
    int i;
    int ch;

    while ((ch = getchar()) != EOF && !isspace(ch))
        *str++ = ch;
    *str = '\0';
    if (ch == EOF)
        return NULL;
    else
    {
        while (ch != '\n')
            ch = getchar();
        return str;
    }
}

PE 11-5

/* Programming Exercise 11-5 */
#include <stdio.h>
#define LEN 80
int is_within(const char * str, char c);
int main(void)
{
    char input[LEN];
    char ch;
    int found;;
    
    printf("Enter a string: ");
    while (gets(input) && input[0] != '\0')
    {
        printf("Enter a character: ");
        ch = getchar();
        while (getchar() != '\n')
            continue;
        found = is_within(input, ch);
        if (found == 0)
            printf("%c not found in string.\n", ch);
        else
            printf("%c found in string %s\n", ch, input);
        printf("Next string: ");
    }
    puts("Done.\n");
    
    return 0;
}

int is_within(const char * str, char ch)
{
    while (*str != ch && *str != '\0')
        str++;
    return *str;   /* = 0 if \0 reached, non-zero otherwise */
}

PE 11-7

/* Programming Exercise 11-7 */
#include <stdio.h>
#define LEN 20
char * string_in(const char * s1, const char * s2);
int main(void)
{
    char orig[LEN] = "transportation";
    char * find;
        
    puts(orig);
    find = string_in(orig, "port");
    if (find)
        puts(find);
    else
        puts("Not found");
    find = string_in(orig, "part");
    if (find)
        puts(find);
    else
        puts("Not found");
    
    return 0;
}

#include <string.h>
char * string_in(const char * s1, const char * s2)
{
    int l2 = strlen(s2);
    int tries;            /* maximum number of comparisons    */
    int nomatch = 1;    /* set to 0 if match is found        */
    
    tries = strlen(s1) + 1 - l2;
    if (tries > 0)
        while (( nomatch = strncmp(s1, s2, l2)) && tries--)
            s1++;
    if (nomatch)
        return NULL;
    else
        return (char *) s1;  /* cast const away */
}

PE 11-9

/* Programming Exercise 11-9 */
#include <stdio.h>
#define LEN 81
int drop_space(char * s);
int main(void)
{
    char orig[LEN];
    
    while (gets(orig) && orig[0] != '\0')
    {    
        drop_space(orig);
        puts(orig);    
    }
    puts("Bye!");
    return 0;
}

int drop_space(char * s)
{
    int ct = 0;
    char * pos;
    while (*s)     /* or while (*s != '\0') */
    {
        if (*s == ' ')
        {
            pos = s;
            do
            {
                *pos = *(pos + 1);
                pos++;
            } while (*pos);
        }
        else
            s++;
    }
        
}

PE 11-11

/* pe11-11.c -- counts words and certain characters */
/* Programming Exercise 11-11                       */
#include <stdio.h>
#include <ctype.h>       // for isspace()  
#include <stdbool.h>     // for bool, true, false          
int main(void)
{
   char c;               // read in character 
   int low_ct = 0;       // number of lowercase characters     
   int up_ct = 0;        // number of uppercase characters     
   int dig_ct = 0;       // number of digits          
   int n_words = 0;      // number of words 
   int punc_ct = 0;      // number of punctuation marks        
   bool inword = false;  // == true if c is in a word  

   printf("Enter text to be analyzed (EOF to terminate):\n");
   while ((c = getchar()) != EOF)
   {
        if (islower(c))
           low_ct++;
        else if (isupper(c))
           up_ct++;
        else if (isdigit(c))
           dig_ct++;
        else if (ispunct(c))
           punc_ct++;
      if (!isspace(c) && !inword)
      {
         inword = true;  // starting a new word 
         n_words++;      // count word          
      }
      if (isspace(c) && inword)
         inword = false; // reached end of word
   }
   printf("\nwords = %d, lowercase = %d, uppercase = %d, "
          "digits = %d, punctuation = %d\n",
           n_words,low_ct,up_ct, dig_ct, punc_ct);