明解C語言 入門篇 第八章答案

練習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));

}

練習8-2

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


int main() {
    int a, b, c, d;
    int max1, max2;
    printf("請輸入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));  //這個表達式的意思是先求出a，b一組和c，d一組中的較大值，再比較兩個較大值求最大值
    printf("最大值是%d", max1);
    putchar('\n');
    max2 = max(max(max(a, b), c), d);  //意思是依次比較a和b的較大值，再用較大值依次比較c，d，而求出最大值
    printf("最大值是%d", max2);

}

練習8-3

#include <stdio.h>
#define swap(int,a,b) {int temp;temp = a;x = y;y = temp;}
int main(void){
    int x = 5;
    int y = 10;
    swap(int, x, y);
    printf("x = %d\ny = %d\n", x, y);
    return 0;
}

練習8-4

#include <stdio.h>
#define number 6

void bsort(int n, int v[]) {
    int i, j;
    for (i = 0; i < n - 1; i++) {
        for (j = n - 1; j > i; j--) {
            if (v[j - 1] < v[j]) {
                int tem = v[j];
                v[j] = v[j - 1];
                v[j - 1] = tem;
            }
        }
    }
}


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

    for (i = 0; i < number; i++) {
        printf("v[%d]=", i);
        scanf("%d", &v[i]);
    }
    putchar('\n');

    bsort(number, v);
    for (i = 0; i < number; i++)
    {
        printf("v[%d]=%d\n", i, v[i]);
    }

}

練習 8-5

.......

練習8-6

#include <stdio.h>

int factorial(int n) {
    int i ;
    int sum = 1;
    for (i = 1; i <= n; i++) {
        sum*=i;
    }
    return sum;
}
int main() {
    int x;
    printf("請輸入一個數:");
    scanf("%d", &x);
    printf("它的階乘是:%d", factorial(x));
}

練習8-7

#include <stdio.h>

int factorial(int n)
{
    if (n > 0)
        return n * factorial(n - 1);
    else
        return 1;
}

int combination(int n, int r) {

    if (n > 0)
        return  factorial(n) / (factorial(r) * factorial(n - r));
    else
        return 1;
}
int main() {
    int n;
    int r;
    printf("n=");
    scanf("%d", &n);
    printf("r=");
    scanf("%d", &r);
    printf("%d", combination(n, r));
}

練習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 0;
}

練習8-9

/*---計算標準輸入中出現的行數---*/

#include <stdio.h>

int main(void)
{
    int ch, i = 0;

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

    return 0;

}

練習8-10

#include <stdio.h>

int main(void)
{
    int i, ch,j;
    int cnt[10] = { 0 };

    while ((ch = getchar()) != EOF) {
        if (ch >= '0' && ch <= '9')
            cnt[ch - '0']++;

    }
    puts("數字字符的出現次數");
    for (i = 0; i < 10; i++) {
        printf("'%d':", i);
        for (j = 0; j < cnt[i]; j++) {
            putchar('*');
            
        }putchar('\n');
    }
    return 0;
}