1.略
2.代码如下：
#include <stdio.h> #include <ctype.h> int isChar(char c) { if (isalpha(c) || isdigit(c)) { return c; } return 0; } int main() { printf("请输入一个字符："); char c; scanf("%c", &c); printf("%d", isChar(c)); return 0; }3.代码如下：
#include <stdio.h> int isPrime(int n) { for (int i = 2; i < n; i++) { if (n % i == 0) { return 0; } } return 1; } int main() { printf("请输入两个整数："); int m, n; scanf("%d %d", &m, &n); for (int i = m; i <= n; i++) { if (isPrime(i)) { printf("%d ", i); } } return 0; }4.代码如下(对题意稍有调整)：
#include <stdio.h> double fun(int x, int n) { double result = 1, temp = 1; int num = 1; for (int i = 1; i <= n; i++) { num *= i; temp *= x; result += (temp / num); } return result; } int main() { printf("请分别输入n和x："); int n, x; scanf("%d %d", &n, &x); printf("%lf", fun(x, n)); return 0; }5.代码如下：
#include <stdio.h> int max_fun(int a, int b) { int temp; while (b > 0) { temp = a % b; a = b; b = temp; } return a; } int min_fun(int a, int b) { return a * b / max_fun(a, b); } int main() { printf("请输入两个正整数："); int a, b; scanf("%d %d", &a, &b); printf("最大公约数为：%d\n最小公倍数为：%d\n", max_fun(a, b), min_fun(a, b)); return 0; }6.代码如下：
#include <stdio.h> void fun(int a[], int n, int x) { for (int i = 0; i < n; i++) { if (a[i] != x) { printf("%d ", a[i]); } } } int main() { int a[5] = {1, 2, 3, 4, 5}; fun(a, 5, 3); return 0; }7.代码如下：
#include <stdio.h> int max_a(int a[], int n) { int max = a[0]; for (int i = 0; i < n; i++) { if (a[i] > max) { max = a[i]; } } return max; } int min_a(int a[], int n) { int min = a[0]; for (int i = 0; i < n; i++) { if (a[i] < min) { min = a[i]; } } return min; } int ave_a(int a[], int n) { int sum = 0; for (int i = 0; i < n; i++) { sum += a[i]; } return sum / n; } int main() { int a[10] = {3, 1, -3, 10000, 4, 333, -300, 2, 6, 10}; printf("最大值为：%d\n最小值为：%d\n平均值为：%d\n", max_a(a, 10), min_a(a, 10), ave_a(a, 10)); return 0; }8.代码如下：
#include <stdio.h> // 加密 int encrypt(int num) { int a, b, c, d = num; a = d / 1000; d %= 1000; b = d / 100; d %= 100; c = d / 10; d %= 10; a = (a+5)%10; b = (b+5)%10; c = (c+5)%10; d = (d+5)%10; return d*1000+c*100+b*10+a; } int main() { int num = 1234; int cipher = encrypt(num); printf("加密后的密文是：%d\n", cipher); // 加密算法和解密算法完全一样 printf("解密后的明文是：%d\n", encrypt(cipher)); return 0; }9.代码如下(没做越界检查)：
#include <stdio.h> /** * 复制子串 * @param str1 * @param m 从0开始 * @param n 复制的长度 * @param str2 */ void str_mid(char str1[], int m, int n, char str2[]) { for (int i = 0; i < n; i++) { str2[i] = str1[m+i]; } } int str_len(char s[]) { int counter = 0; char c = s[0]; while (c != '\0') { c = s[++counter]; } return counter; } int main() { char str1[] = "goodmorning", str2[10]; int m = 1, n = 3; str_mid(str1, m, n, str2); printf("原字符串为：%s，长度为%d\n", str1, str_len(str1)); printf("复制后的子串为：%s，长度为%d\n", str2, str_len(str2)); return 0; }10.代码如下(非递归)：
#include <stdio.h> int fib(int n) { int prev = 0, next = 1, temp; if (n == 0) { return prev; } else if (n == 1) { return next; } for (int i = 2; i <= n; i++) { temp = prev + next; prev = next; next = temp; } return next; } int main() { int n = 10; printf("第%d个斐波那契数是%d", n, fib(n)); return 0; }Chapter08 地址操作与指针
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