实验三

任务一

#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;
}

 问题一：功能：将分数转为等级；形参：int；返回值：char

问题二："A"是字符串，赋值给 char 类型类型不匹配。无 break，case 穿透，逻辑错误

任务二

#include <stdio.h>
int sum_digits(int n);

int main() {
    int n, 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;
        n /= 10;
    }
    return ans;
}

 

问题1：计算整数各位数字之和
问题2：递归版本可以实现；区别：原代码：迭代循环；递归版：把问题拆分为 个位 + 剩余位和

任务三

#include <stdio.h>
int power(int x, int n);

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

int power(int x, int n) {
    int t;
    if(n == 0)
        return 1;
    else if(n % 2 == 1)
        return x * power(x, n - 1);
    else {
        t = power(x, n / 2);
        return t * t;
    }
}

 

问题1：递归计算 x 的 n 次幂
是递归函数；数学公式：power(x, 0) = 1
n 奇数：power (x,n) = x * power (x,n-1)
n 偶数：power (x,n) = power (x,n/2)²

任务四

#include <stdio.h>
int classify_triangle(int a, int b, int c);

int main() {
    int a, b, c;
    while(scanf("%d%d%d", &a, &b, &c) != EOF) {
        int r = classify_triangle(a, b, c);
        switch(r) {
            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;
        }
    }
    return 0;
}

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

 任务五

#include <stdio.h>
int func(int n, int m);

int main() {
    int n, m;
    while(scanf("%d%d", &n, &m) != EOF) {
        int ans = func(n, m);
        printf("n=%d, m=%d, ans=%d\n", n, m, ans);
    }
    return 0;
}

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

#include <stdio.h>
int func(int n, int m);

int main() {
    int n, m;
    while(scanf("%d%d", &n, &m) != EOF) {
        int ans = func(n, m);
        printf("n=%d, m=%d, ans=%d\n", n, m, ans);
    }
    return 0;
}

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

 任务六

#include <stdio.h>
int gcd(int a, int b, int c);

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

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

 任务七

#include <stdio.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) {
    for(int i = n; i >= 1; --i) {
        for(int j = 0; j < n - i; ++j)
            printf("\t");
        for(int j = 0; j < i; ++j)
            printf("<H> ");
        printf("\n");

        for(int j = 0; j < n - i; ++j)
            printf("\t");
        for(int j = 0; j < i; ++j)
            printf("II ");
        printf("\n\n");
    }
}