C:A big homework of C language lesson

menu.c

#include<stdio.h>
#include<math.h>

void clearbuffer(void) {
    int z;
    while ((z = getchar()) != '\n' && z != EOF);
}

long int narcissistic_number(long int x) {
    long int a, sum=0, t=x;
    while (x != 0) {
        a = x%10;
        sum += a*a*a;
        x /= 10;
    }
    if (t == sum) return 0;
    else return -1;
}

int lower_char(int c) {
    if (c >= 65 && c <= 90)
        return c + 32;
    else if (c == 10) return 10;
    else return -1;
}

long int prime(long int x) {
    long int i;
    for(i=2; i <= sqrt((double)x); i++) {
        if (x%i == 0) return -1;
    }
    return 0;
}

long int gcd(long int x, long int y) {
    long int r;
    if (y > x) {
        x ^= y;
        y ^= x;
        x ^= y;
    }
    r = x%y;
    while (r != 0) {
        x = y;
        y = r;
        r = x%y;
    }
    return y;
}

long int max(long int x, long int y, long int z) {
    if (x >= y && x >= z) return x;
    else if (y >= x && y >= z) return y;
    else return z;
}

long int factorial(long int x) {
    long int s = 1;
    for (; x > 0; x--) {
        s *= x;
    }
    return s;
}

long int times_five(long int x, long int y) {
    long int a, i=0;
    while (x != 0) {
        a = x%10;
        if (y == a) i++;
        x /= 10;
    }
    return i;
}

long int judge_add_mult(long int x) {
    long int s=0, m=1, a;
    while (x != 0) {
        a = x%10;
        s += a;
        m *= a;
        x /= 10;
    }
    if (s == m) return 0;
    else return -1;
}

void triangle(long int x) {
    long int i, j;
    for (i=0; i<x; i++) {
        for (j=0; j<10+x-i; j++) printf(" ");
        for (j=0; j<2*i-1; j++) printf("*");
        printf("\n");
    }
}

int main(void) {
    char c;
    long int x, y, z;
    int err, h;
    printf("本程序可以完成某些数学计算：\n"
        "******************************************************\n"
        "*  1  判断一个数是否为水仙花数                       *\n"
        "*  2  判断一个数是否为素数                           *\n"
        "*  3  求两个数的最大公约数                           *\n"
        "*  4  求三个数的最大值                               *\n"
        "*  5  求一个数的阶乘                                 *\n"
        "*  6  输出一个5位数中某数字出现的次数                *\n"
        "*  7  判断一个数的各个位上数字之和与数字之积是否相等 *\n"
        "*  8  打印输出n行三角形                              *\n"
        "*  9  将输入的n个大写字母转换成小写字母              *\n"
        "*  0  退出                                           *\n"
        "******************************************************\n");
    do {
        printf("请按菜单进行选择(0-9)：\n");
        scanf("%c", &c);
        if (c == '\n') continue;
        clearbuffer();
        if (c < '0' || c > '9') {
            printf("Error:无此菜单项，请重新输入！\n");
            continue;
        } else if (c == '0') {
            do {
                printf("你确定退出吗？(Y/n)\n");
                scanf("%c", &c);
            } while (!(c == 'y' || c == 'Y' || c == 'N' || c == 'n' || c == '\n'));
            if (c == 'y' || c == 'Y' || c == '\n') {
                printf("欢迎再次使用，Byebye!\n");
                if (c == '\n') break;
            }
            else if (c == 'n' || c == 'N') {
                clearbuffer();
                continue;
            }
        } else {
            do {
                err = 0;
                switch(c) {
                    case '3':
                        printf("请输入两个正整数：\n");
                        scanf("%ld%ld", &x, &y);
                        clearbuffer();
                        if (x > 0 && y > 0) {
                            z = gcd(x, y);
                            printf("%ld和%ld的最大公约数为%ld\n", x, y, z);
                        } else {
                            printf("Error:输入的数必须为正整数！\n");
                        }
                        break;
                    case '4':
                        printf("请输入三个整数：\n");
                        scanf("%ld%ld%ld", &x, &y, &z);
                        clearbuffer();
                        x = max(x, y, z);
                        printf("最大值为%ld\n", x);
                        break;
                    case '6':
                        printf("请输入一个五位整数：\n");
                        scanf("%5ld", &x);
                        clearbuffer();
                        printf("请输入指定的数字：\n");
                        scanf("%1ld", &y);
                        clearbuffer();
                        z = times_five(x, y);
                        printf("数字%ld在%ld出现的次数为%ld次。\n", y, x, z);
                        break;
                    case '9':
                        printf("请输入大写字母(直接按 Enter 返回主菜单)：\n");
                        for (y=1; (h = getchar()) != '\n'; y++) {
                            if ((h >= 65 && h <= 90) || h == 10) {
                                h = lower_char(h);
                                putchar(h);
                            } else {
                                clearbuffer();
                                printf("\nError:第%ld个字符输入有误，请重新输入！", y);
                                err = 1;
                                break;
                            }
                        }
                        if (y > 1 || h != 10) printf("\n");
                        break;
                    default:
                        printf("请输入一个整数：\n");
                        scanf("%ld", &x);
                        clearbuffer();
                        switch(c) {
                            case '1':
                                if (x > 0) {
                                    y = narcissistic_number(x);
                                    if (y == 0) printf("%ld是水仙花数。\n", x);
                                    else printf("%ld不是水仙花数。\n", x);
                                }
                                else {
                                    printf("Error:输入的数必须为正整数！\n");
                                    err = 1;
                                }
                                break;
                            case '2':
                                if (x > 1) {
                                    y = prime(x);
                                    if (y == 0) printf("%ld是素数。\n", x);
                                    else printf("%ld不是素数。\n", x);
                                } else {
                                    printf("Error:输入的整数必须大于1！\n");
                                    err = 1;
                                }
                                break;
                            case '5':
                                if (x >= 0) {
                                    y = factorial(x);
                                    printf("%ld!=%ld\n", x, y);
                                } else {
                                    printf("Error:输入的数必须为非负整数！\n");
                                    err = 1;
                                }
                                break;
                            case '7':
                                if (x > 0) {
                                    y = judge_add_mult(x);
                                    if (y == 0) printf("%ld的各个位上数字之和与数字之积相等。\n", x);
                                    else printf("%ld的各个位上数字之和与数字之积不相等。\n", x);
                                } else {
                                    printf("Error:输入的数必须为正整数！\n");
                                    err = 1;
                                }
                                break;
                            case '8':
                                if (x > 2)
                                    triangle(x);
                                else {
                                    printf ("Error:输入的整数必须大于2，否则无法生成三角形！\n");
                                    err = 1;
                                }
                                break;
                        }
                        break;
                }
            } while (err == 1);
        }
    } while (!(c == 'y' || c == 'Y'));
    printf("按回车键退出...");
    getchar();
    return 0;
}