实验3

task1

#include <stdio.h>

char score_to_grade(int score);

int main(){
    int score;
    char grade;
    
    while(scanf("%d",&score) != EOF){
        grade = score_to_grade(score);
        printf("分数：%d,等级：%c\n\n",score, grade);
    }
    
    return 0;
}


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;
}

问题1：根据分数十分位来判断得到的等级，整型。

问题2：得到A等级之后不会停，一直输入bcd等级。

task2

#include <stdio.h>

int sum_digits(int n); 

int main() {
    int n;
    int ans;

    while(printf("Enter n: "), scanf("%d", &n) != EOF) {
       ans = sum_digits(n); 
       printf("n = %d, ans = %d\n\n", n, ans);
    }

    return 0;
}

int sum_digits(int n) {
    int ans = 0;

    while(n != 0) {
       ans += n % 10;2049
       n /= 10;
    }

    return ans;
}

问题1：计算并返回一个整数n各位数字之和

问题2：可以，原来的是迭代 改后的是递归

task3

#include <stdio.h>

int power(int x, int n);

int main() {
    int x, n;
    int ans;

    while(printf("Enter x and n: "), scanf("%d%d", &x, &n) != EOF) {
        ans = power(x, n); 
        printf("n = %d, ans = %d\n\n", n, ans);
    }
    
    return 0;
}

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;
    }
}

问题1：计算x的n次方

问题2：

 task4

#include <stdio.h>
#include <stdlib.h>

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

int main()
{
    int a, b, c, ans;
    while (scanf("%d%d%d", &a, &b, &c) != EOF)
    {
        ans = classify_triangle(a, b, c);
        switch (ans)
        {
            case 0: printf("不能构成三角形\n"); break;
            case 1: printf("普通三角形\n"); break;
            case 2: printf("等边三角形\n"); break;
            case 3: printf("等腰三角形\n"); break;
            case 4: printf("直角三角形\n"); break;
        }
    }
    system("pause");
   
    return 0;
}

int classify_triangle(int a, int b, int c)
{
    if (a + b <= c || a + c <= b || b + c <= a)
        return 0;
    else if (a == b && b == c)
        return 2;
    else if (a == b || a == c || b == c)
        return 3;
    else if (a*a + b*b == c*c || a*a + c*c == b*b || b*b + c*c == a*a)
        return 4;
    else 
        return 1;
}

task5

迭代

#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); 
        printf("n = %d, m = %d, ans = %d\n\n", n, m, ans);
    } 

    return 0;
}
int func(int n, int m){
    if (m == 0 || n == m) return 1;
    long long ans = 1; 
    for (int i = 1; i <= m; i++) {
        ans = ans * (n - i + 1) / i;
    }
    return (int)ans;
    
} 

递归

#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); 
        printf("n = %d, m = %d, ans = %d\n\n", n, m, ans);
    } 

    return 0;
}
int func(int n, int m){
     if (m == 0 || n == m) {
        return 1;
    }
    if (m > n) {
        return 0; 
    }
    return func(n - 1, m) + func(n - 1, m - 1);
    
} 

task6

#include <stdio.h>

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

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

    while(scanf("%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 i=0;
    if(a<b<c||a<c<b)
        i=a;
    else if(b<a<c||b<c<a) 
        i=b;
    else
        i=c;
    for(;i>=1;--i)
    {
    if(a%i==0&&b%i==0&&c%i==0)
        return i;
    }
}

task7

#include <stdio.h>
#include <stdlib.h>

void print_charman(int n);

int main() {
    int n;
    
    printf("Enter n: ");
    scanf("%d",&n);
    print_charman(n);
    
    return 0;
}

void print_charman(int n) {
      int i=1;
    for (int i = 1; i <= n; i++) {
        int k=2*(n-i)+1;
        int j=1;
        for (int j = 1; j < i; j++) {
            printf("\t");
        }
        for (int j = 1; j <= k; j++) {
            printf(" O \t");
        }
        printf("\n");
        for (int j = 1; j < i; j++) {
            printf("\t");
        }
        for (int j = 1; j <=k; j++) {
            printf("<H>\t");
        }
        printf("\n");
        for (int j = 1; j < i; j++) {
            printf("\t");
        }
        for (int j = 1; j <= k; j++) {
            printf("I I\t");
        }
        printf("\n");
    }