实验三

`#define _CRT_SECURE_NO_WARNINGS

include <stdio.h>

char score_to_grade(int score); // 函数声明
int main() {
int score;
char grade;
while (scanf("%d", &score) != EOF) {
grade = score_to_grade(score); // 函数调用
printf("分数: %d, 等级: %c\n\n", score, grade);
}
return 0;
}
// 函数定义
char score_to_grade(int score) {
char ans;
switch (score / 10) {
case 10:
case 9: ans = 'A'; break;
case 8: ans = 'B'; break;
case 7: ans = 'C'; break;
case 6: ans = 'D'; break;
default: ans = 'E';
}
return ans;
}`


1.定义一个函数
2.会一直往下运行不跳出循环

`#define _CRT_SECURE_NO_WARNINGS

include <stdio.h>

int sum_digits(int n); // 函数声明
int main() {
int n;
int ans;
while (printf("Enter n: "), scanf("%d", &n) != EOF) {
ans = sum_digits(n); // 函数调用
printf("n = %d, ans = %d\n\n", n, ans);
}
return 0;
}
// 函数定义
int sum_digits(int n) {
int ans = 0;
while (n != 0) {
ans += n % 10;
n /= 10;
}
return ans;
}`

1.调换顺序
2.能，一个递归一个迭代

`#define _CRT_SECURE_NO_WARNINGS

include <stdio.h>

int power(int x, int n); // 函数声明
int main() {
int x, n;
int ans;
while (printf("Enter x and n: "), scanf("%d%d", &x, &n) != EOF) {
ans = power(x, n); // 函数调用
printf("n = %d, ans = %d\n\n", n, ans);
}
return 0;
}
// 函数定义
int power(int x, int n) {
int t;
if (n == 0)
return 1;
else if (n % 2)
return x * power(x, n - 1);
else {
t = power(x, n / 2);
return t * t;
}
}`

1.将x乘y次
2.

`#define _CRT_SECURE_NO_WARNINGS

include <stdio.h>

include <math.h>

int is_prime(int n) {
if (n < 2) {
return 0;
}
for (int i = 2; i <= sqrt(n); i++) {
if (n % i == 0) {
return 0;
}
}
return 1;
}

int main() {
int count = 0;
printf("100以内的孪生素数:\n");
for (int i = 1; i < 99; i++) {
if (is_prime(i) && is_prime(i + 2)) {
printf("%d %d\n", i, i + 2);
count++;
}
}
printf("100以内的孪生素数共有%d个\n", count);
return 0;
}`

`#define _CRT_SECURE_NO_WARNINGS

include <stdio.h>

int count = 0;
void hanoi(int n, char source, char target, char auxiliary) {
if (n == 1) {
printf("1: %c --> %c\n", source, target);
count++;
return;
}
hanoi(n - 1, source, auxiliary, target);
printf("%d: %c --> %c\n", n, source, target);
count++;
hanoi(n - 1, auxiliary, target, source);
}

int main() {
int a=0;
while (scanf("%d", &a) != EOF) {
int n_values[] = { a }; // 可按需修改输入值
int i;

    for (i = 0; i < sizeof(n_values) / sizeof(n_values[0]); i++) {

        hanoi(n_values[i], 'A', 'C', 'B');
        printf("一共移动了%d次.\n", count);
        count = 0;
    }
  
}  
return 0;

}`

`#define _CRT_SECURE_NO_WARNINGS

include <stdio.h>

int func(int n, int m); // 函数声明
int main() {
int n, m;
int ans;
while (scanf("%d%d", &n, &m) != EOF) {
ans = func(n, m); // 函数调用
printf("n = %d, m = %d, ans = %d\n\n", n, m, ans);
}
return 0;
}
int func(int n, int m) {
int i = 0;
int sum = 1;
if (n > m && m!=0) {
for (i = 0; i >= m; --n, --m)
sum = n / m;
}
if (m== 0||n/m==1) {
sum = 1;
}
else {
sum = 0;
}
return sum;
}
#define _CRT_SECURE_NO_WARNINGS

include <stdio.h>

int func(int n, int m);
int main(){
int n, m;
int ans;
while (scanf("%d%d", &n, &m) != EOF) {
ans = func(n, m); // 函数调用
printf("n = %d, m = %d, ans = %d\n\n", n, m, ans);
}
return 0;
}
int func(int n, int m) {
if (m == 0 || m == n) {
return 1;
}if (m > n) {
return 0;
}
else {
return func(n - 1, m) + func(n - 1, m - 1);
}
}
`

`#define _CRT_SECURE_NO_WARNINGS

include <stdio.h>

int gcd(int a, int b, int c);

int main() {
int a, b, c;
int ans;

while (scanf_s("%d%d%d", &a, &b, &c) != EOF) {
    ans = gcd(a, b, c);
    printf("最大公约数: %d\n\n", ans);
}
return 0;

}

int gcd(int a, int b, int c) {
int min = a;
if (b < min) min = b;
if (c < min) min = c;

for (int i = min; i >= 1; i--) {
    if (a % i == 0 && b % i == 0 && c % i == 0) {
        return i;
    }
}
return 1;

}`