明解C语言 入门篇 第八章答案

练习8-1

#include<stdio.h>
#define diff(x,y)(x-y)

int main() {
    int x;
    int y;
    printf("x=");
    scanf("%d", &x);
    printf("y=");
    scanf("%d", &y);
    printf("%d", diff(x, y));

}

练习8-2

#include <stdio.h>
#define max(x,y) ((x)>(y)?x:y)

int main() {
    int a, b, c, d;
    int max1, max2;
    printf("请输入a b c d 的值:\n");
    scanf("%d",&a);
    scanf("%d", &b);
    scanf("%d", &c);
    scanf("%d", &d);
    max1 = max(max(a, b), max(c, d));  //这个表达式的意思是先求出a，b一组和c，d一组中的较大值，再比较两个较大值求最大值
    printf("最大值是%d", max1);
    putchar('\n');
    max2 = max(max(max(a, b), c), d);  //意思是依次比较a和b的较大值，再用较大值依次比较c，d，而求出最大值
    printf("最大值是%d", max2);

}

练习8-3

#include <stdio.h>
#define swap(int,a,b) {int temp;temp = a;x = y;y = temp;}
int main(void){
    int x = ;
    int y = ;
    swap(int, x, y);
    printf("x = %d\ny = %d\n", x, y);
    return ;
}

练习8-4

#include <stdio.h>
#define number 6

void bsort(int n, int v[]) {
    int i, j;
    for (i = ; i < n - ; i++) {
        for (j = n - ; j > i; j--) {
            if (v[j - ] < v[j]) {
                int tem = v[j];
                v[j] = v[j - ];
                v[j - ] = tem;
            }
        }
    }
}

int main() {
    int i;
    int v[number];

    for (i = ; i < number; i++) {
        printf("v[%d]=", i);
        scanf("%d", &v[i]);
    }
    putchar('\n');

    bsort(number, v);
    for (i = ; i < number; i++)
    {
        printf("v[%d]=%d\n", i, v[i]);
    }

}

练习 8-5

#include <stdio.h>
enum season{春,夏,秋,冬,Invaild};

enum season select(void) {
    int tmp;
    do {
        printf("0...春   1...夏   2...秋   3...冬   4...结束");
        scanf("%d", &tmp);
    } while (tmp< 春 || tmp> Invaild);
    return tmp;
}

int main(void) {
    enum season selected;
    do {
        switch (selected=select())
        {
        case 春:break;
        case 夏:break;
        case 秋:break;
        case 冬:break;

        }

    } while (selected != Invaild);
    return ;

}

练习8-6

#include <stdio.h>

int factorial(int n) {
    int i ;
    int sum = ;
    for (i = ; i <= n; i++) {
        sum*=i;
    }
    return sum;
}
int main() {
    int x;
    printf("请输入一个数:");
    scanf("%d", &x);
    printf("它的阶乘是:%d", factorial(x));
}

练习8-7

#include <stdio.h>

int factorial(int n)
{
    if (n > )
        return n * factorial(n - );
    else
        return ;
}

int combination(int n, int r) {

    if (n > )
        return  factorial(n) / (factorial(r) * factorial(n - r));
    else
        return ;
}
int main() {
    int n;
    int r;
    printf("n=");
    scanf("%d", &n);
    printf("r=");
    scanf("%d", &r);
    printf("%d", combination(n, r));
}

练习8-8

#include <stdio.h>
int gcd(int x, int y)
{
    int z;
    if (x != y)
    {
        if (x > y)
            x -= y;
        else
            y -= x;
        z = gcd(x, y);
    }
    else
        z = x;
    return z;
}
int main(void)
{
    int x, y;
    printf("x:");
    scanf("%d", &x);
    printf("y:");
    scanf("%d", &y);
    printf("gcd(%d,%d) = %d\n", x, y, gcd(x, y));
    return ;
}

练习8-9

/*---计算标准输入中出现的行数---*/

#include <stdio.h>

int main(void)
{
    int ch, i = ;

    while ((ch = getchar()) != EOF) {
        if (ch == '\n')    i++;
    }
    printf("%d", i);

    return ;

}

练习8-10

#include <stdio.h>

int main(void)
{
    int i, ch,j;
    int cnt[] = {  };

    while ((ch = getchar()) != EOF) {
        if (ch >= '' && ch <= '')
            cnt[ch - '']++;

    }
    puts("数字字符的出现次数");
    for (i = ; i < ; i++) {
        printf("'%d':", i);
        for (j = ; j < cnt[i]; j++) {
            putchar('*');

        }putchar('\n');
    }
    return ;
}