第六章 编程练习

6-1

#include <stdio.h>
#define SIZE 26

int main(int argc, char const *argv[])
{
    char lcase[SIZE];
    int i;
    for (i = 0; i < SIZE; i++){
        lcase[i] = (char)((int)'a' + i); //可以直接lcase[i] = 'a'+i
    }
    for (i = 0; i < SIZE; i++)
        printf("%c", lcase[i]);

    return 0;
}

6-2

#include <stdio.h>

int main(int argc, char const *argv[])
{
    int i,j;
    for (i = 1; i <= 5; i++){
        for (j = 1; j <= i; j++)
        {
            printf("$");
        }
        printf("\n");
    }

    return 0;
}

/* 
$
$$
$$$
$$$$
$$$$$

*/

6-3

#include <stdio.h>

int main(int argc, char const *argv[])
{
    int i,j;
    char c;
    for (i = 1; i <= 6; i++){
        for (j = 1, c = 'F'; j <= i; j++, c--)
        {
            printf("%c", c);
        }
        printf("\n");
    }

    return 0;
}

/* 
F
FE
FED
FEDC
FEDCB
FEDCBA

*/

6-4

#include <stdio.h>

int main(int argc, char const *argv[])
{
    int i,j;
    char c = 'A';
    for (i = 1; i <= 6; i++){
        for (j = 1; j <= i; j++, c++)
        {
            printf("%c", c);
        }
        printf("\n");
    }

    return 0;
}

/* 
A
BC
DEF
GHIJ
KLMNO
PQRSTU

*/

6-5

#include <stdio.h>

int main(int argc, char const *argv[])
{
    int i,j,n;
    char c;

    printf("Enter a capital letter(like E):");
    scanf("%c", &c);
    n = c - 'A' + 1;
    for (i = 1; i <= n; i++){
        for (j = 1; j <= ((2*n-1)-(2*i-1))/2; j++) printf(" ");
        for (j = 0, c = 'A'; j < i; c++, j++) printf("%c", c);
        for (j = 0, c-=2; j < (i-1); c--, j++) printf("%c", c);
        printf("\n");
    }

    return 0;
}

/* 
Enter a capital letter(like E):E
    A
   ABA
  ABCBA
 ABCDCBA
ABCDEDCBA

*/

6-6

#include <stdio.h>

int main(int argc, char const *argv[])
{
    int top,bot;
    int i;

    printf("Enter a top num:");
    scanf("%d", &top);
    printf("Enter a bottom num:");
    scanf("%d", &bot);
    printf("%5s %5s %5s\n", "n", "square", "cube");

    for (i = bot; i <= top; i++){
        printf("%5d %5d %5d\n", i, i*i, i*i*i);
    }

    return 0;
}

/* 
Enter a top num:5
Enter a bottom num:1
    n square  cube
    1     1     1
    2     4     8
    3     9    27
    4    16    64
    5    25   125

*/

6-7

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

int main(int argc, char const *argv[])
{
    char word[20];
    int i;

    printf("Enter a word:");
    scanf("%s", word);

    for (i = strlen(word)-1; i >= 0; i--){
        printf("%c", word[i]);
    }

    return 0;
}

/* 
Enter a word:god
dog
*/

6-8

#include <stdio.h>

int main(int argc, char const *argv[])
{
    float a, b;

    printf("Enter two different float number:");
    while (scanf("%f %f", &a, &b) == 2){   //printf()中float和double都用 %f；scanf()中float用 %f,double用 %lf
        printf("(%.3g-%.3g)/(%.3g*%.3g) = %.3g\n", a, b, a, b, (a-b)/(a*b));  //%.3g表示小数点后面三位有效数字
        printf("Enter two different float number:");
    }
    return 0;
}

/* 
Enter two different float number:3 2
(3-2)/(3*2) = 0.167
Enter two different float number:6.2 8.9
(6.2-8.9)/(6.2*8.9) = -0.0489
Enter two different float number:q

*/

 6-9

#include <stdio.h>

float calc(float m, float n);

int main(int argc, char const *argv[])
{
    float a, b;

    printf("Enter two different float number:");
    while (scanf("%f %f", &a, &b) == 2){   //printf()中float和double都用 %f；scanf()中float用 %f,double用 %lf
        printf("(%.3g-%.3g)/(%.3g*%.3g) = %.3g\n", a, b, a, b, calc(a, b));  //%.3g表示小数点后面三位有效数字
        printf("Enter two different float number:");
    }
    return 0;
}

float calc(float m, float n){
    return (m-n)/(m*n);
}
/* 
Enter two different float number:3 2
(3-2)/(3*2) = 0.167
Enter two different float number:6.2 8.9
(6.2-8.9)/(6.2*8.9) = -0.0489
Enter two different float number:q

*/

6-10

#include <stdio.h>

int main(int argc, char const *argv[])
{
    int a, b, sum, i;

    printf("Enter a lower integer and a upper integer(like 5 9):");
    scanf("%d %d", &a, &b);

    while (a < b){
        for (sum = 0, i = a; i <= b; i++)
        {
            sum += i*i;
        }
        printf("The sum of the squares form %d to %d is %d\n", a*a, b*b, sum);
        printf("Enter a lower integer and a upper integer(like 5 9):");
        scanf("%d %d", &a, &b);
    }
    printf("Done!");

    return 0;
}

/* 
Enter a lower integer and a upper integer(like 5 9):5 9
The sum of the squares form 25 to 81 is 255
Enter a lower integer and a upper integer(like 5 9):3 25
The sum of the squares form 9 to 625 is 5520
Enter a lower integer and a upper integer(like 5 9):5 5
Done!
*/

6-11

#include <stdio.h>
#define SIZE 8

int main(int argc, char const *argv[])
{
    int num[SIZE];
    int i;

    printf("Enter %d integer:\n", SIZE);
    for (i = 0; i < SIZE; i++)
    {
        scanf("%d", &num[i]);
    }
    printf("The revese sequence of your input number is:\n");
    for (i = SIZE - 1; i >= 0; i--)
    {
        printf("%d ", num[i]);
    }
    printf("\n");

    return 0;
}

/* 
Enter 8 integer:
1
2
33
4
55
66
7
88
The revese sequence of your input number is:
88 7 66 55 4 33 2 1

*/

6-12

#include <stdio.h>
#include <math.h>

int main(int argc, char const *argv[])
{
    int n;
    int i, j;
    float sum;

    printf("Enter how many element you want to be summary(n):");
    scanf("%d", &n);
    while (n > 0){
        for (i = 1, sum = 0; i <= n; sum += 1.0/i, i++);
        printf("when n = %d, 1.0 + 1.0/2.0 + 1.0/3.0 + ... = %f\n", n, sum);

        for (i = 1, j = 1, sum = 0; i <= n; sum += 1.0/i*j, i++, j*=-1);
        printf("when n = %d, 1.0 - 1.0/2.0 + 1.0/3.0 - ... = %f\n", n, sum);

        printf("Enter how many element you want to be summary(n):");
        scanf("%d", &n);
    }

    printf("Done!");

    return 0;
}

/* 
Enter how many element you want to be summary(n):100
when n = 100, 1.0 + 1.0/2.0 + 1.0/3.0 + ... = 5.187378
when n = 100, 1.0 - 1.0/2.0 + 1.0/3.0 - ... = 0.688172
Enter how many element you want to be summary(n):1000
when n = 1000, 1.0 + 1.0/2.0 + 1.0/3.0 + ... = 7.485478
when n = 1000, 1.0 - 1.0/2.0 + 1.0/3.0 - ... = 0.692646
Enter how many element you want to be summary(n):10000
when n = 10000, 1.0 + 1.0/2.0 + 1.0/3.0 + ... = 9.787613
when n = 10000, 1.0 - 1.0/2.0 + 1.0/3.0 - ... = 0.693091
Enter how many element you want to be summary(n):10000000
when n = 10000000, 1.0 + 1.0/2.0 + 1.0/3.0 + ... = 15.403683
when n = 10000000, 1.0 - 1.0/2.0 + 1.0/3.0 - ... = 0.693137
Enter how many element you want to be summary(n):-1
Done!
*/

6-13

#include <stdio.h>
#include <math.h>
#define SIZE 8

int main(int argc, char const *argv[])
{
    int num[SIZE];
    int i;

    for (i = 0; i < SIZE; i++)
    {
        num[i] = pow(2, i+1);
    }
    printf("The element in array are:\n");
    i = 0;
    do{
        printf("%d ", num[i]);
        i++;
    }while(i < SIZE);

    return 0;
}

/* 
The element in array are:
2 4 8 16 32 64 128 256
*/

6-14

#include <stdio.h>
#define SIZE 8

int main(int argc, char const *argv[])
{
    double a[SIZE], b[SIZE];
    int i;
    double sum;

    printf("Enter %d number:\n", SIZE);
    for (i = 0, sum = 0; i < SIZE; i++)
    {
        scanf("%lf", &a[i]);
        sum += a[i];
        b[i] = sum;
    }
    printf("Two array would be listeda as follows:\n");
    for (i = 0; i < SIZE; i++)
    {
        printf("%6.3g", a[i]);
    }
    printf("\n");
      for (i = 0; i < SIZE; i++)
    {
        printf("%6.3g", b[i]);
    }

    return 0;
}

/* 
Enter 8 number:
1.1
2.1
3.1
4.4
5.5
6.6
7
8
Two array would be listeda as follows:
   1.1   2.1   3.1   4.4   5.5   6.6     7     8
   1.1   3.2   6.3  10.7  16.2  22.8  29.8  37.8
*/

6-15-6-18略