选题42、算24小游戏C语言 功能要求： 1）用户注册/登录。 2）随机生成4个1—13的数值，如2，5，6，8。 3）使用加减乘除（可带括号，先加减再乘除）计算能否得24，每个数值只能使用1次且必须使用1次，如（6+2-5）*8。 4）由用户列四则运算式，验证用户算式是否正确，如可得24表示正确并统计，不可得24表示提示计算错误并统计。 5）用户可以输入特殊符号表示无解，若确实无解提示用户正确并统计。若该情况有解，提示用户有解，可继续计算。若用户可放弃有解计算，由系统提示正确答案，并统计。 6）可查看用户累计解正确次数，错误次数，放弃次数。

以下是算24小游戏的C语言实现：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <ctype.h>

#define MAX_ATTEMPT 10

int login(void);
int register_user(void);
int generate_number(int *numbers);
int check_solution(char *expr, int *numbers);
int solve(int *numbers, char *solution);

int main(void)
{
    int choice, numbers[4], result;
    char solution[50];

    srand(time(NULL));

    printf("Welcome to the 24 Game!\n");
    printf("-----------------------\n");

    do {
        printf("1. Login\n");
        printf("2. Register\n");
        printf("3. Quit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                if (login()) {
                    result = generate_number(numbers);
                    if (result) {
                        printf("The numbers are: %d %d %d %d\n", numbers[0], numbers[1], numbers[2], numbers[3]);
                        printf("Enter your solution (use +, -, *, / and parentheses): ");
                        scanf("%s", solution);
                        if (check_solution(solution, numbers)) {
                            printf("Congratulations! You solved it!\n");
                        } else {
                            printf("Sorry, your solution is incorrect.\n");
                        }
                    }
                } else {
                    printf("Login failed. Please try again.\n");
                }
                break;
            case 2:
                if (register_user()) {
                    printf("Registration successful.\n");
                } else {
                    printf("Registration failed. Please try again.\n");
                }
                break;
            case 3:
                printf("Goodbye!\n");
                break;
            default:
                printf("Invalid choice. Please try again.\n");
                break;
        }
    } while (choice != 3);

    return 0;
}

int login(void)
{
    char username[20], password[20], buffer[50];
    FILE *fp;

    printf("Enter your username: ");
    scanf("%s", username);
    printf("Enter your password: ");
    scanf("%s", password);

    fp = fopen("users.txt", "r");
    if (fp == NULL) {
        printf("Error: cannot open file.\n");
        exit(EXIT_FAILURE);
    }

    while (fgets(buffer, sizeof(buffer), fp)) {
        if (sscanf(buffer, "%s %s", username, password) == 2) {
            if (strcmp(username, buffer) == 0 && strcmp(password, buffer + strlen(username) + 1) == 0) {
                fclose(fp);
                return 1;
            }
        }
    }

    fclose(fp);
    return 0;
}

int register_user(void)
{
    char username[20], password[20], buffer[50];
    FILE *fp;

    printf("Enter your username: ");
    scanf("%s", username);
    printf("Enter your password: ");
    scanf("%s", password);

    fp = fopen("users.txt", "a");
    if (fp == NULL) {
        printf("Error: cannot open file.\n");
        exit(EXIT_FAILURE);
    }

    fprintf(fp, "%s %s\n", username, password);
    fclose(fp);

    return 1;
}

int generate_number(int *numbers)
{
    int i;

    for (i = 0; i < 4; i++) {
        numbers[i] = rand() % 13 + 1;
    }

    return solve(numbers, NULL);
}

int check_solution(char *expr, int *numbers)
{
    int i, j, k, l, a, b, c, d;
    char solution[50];
    char operands[] = {'+', '-', '*', '/'};
    char operators[4];

    for (i = 0; i < strlen(expr); i++) {
        if (!isdigit(expr[i]) && expr[i] != '+' && expr[i] != '-' && expr[i] != '*' && expr[i] != '/' && expr[i] != '(' && expr[i] != ')') {
            printf("Invalid character in solution.\n");
            return 0;
        }
    }

    for (i = 0; i < 4; i++) {
        sprintf(solution + strlen(solution), "%d", numbers[i]);
        if (i < 3) {
            sprintf(solution + strlen(solution), "%c", operands[rand() % 4]);
        }
    }

    for (i = 0; i < strlen(expr); i++) {
        if (expr[i] == '(') {
            for (j = i + 1; j < strlen(expr); j++) {
                if (expr[j] == ')') {
                    strncpy(solution + i, expr + i + 1, j - i - 1);
                    solution[j - 1] = '\0';
                    break;
                }
            }
        }
    }

    for (i = 0; i < 4; i++) {
        operators[i] = '\0';
    }

    for (i = 0; i < strlen(solution); i++) {
        if (solution[i] == '+') {
            operators[0]++;
        } else if (solution[i] == '-') {
            operators[1]++;
        } else if (solution[i] == '*') {
            operators[2]++;
        } else if (solution[i] == '/') {
            operators[3]++;
        }
    }

    if (operators[0] < 1 || operators[1] < 1 || operators[2] < 1 || operators[3] < 1) {
        printf("Invalid solution: must use at least one of each operator.\n");
        return 0;
    }

    for (i = 0; i < 24; i++) {
        a = i / 6;
        b = i % 6 / 2;
        c = i % 2;
        d = 6 - a - b - c;

        sprintf(solution, "(%d%c%d)%c(%d%c%d)%c(%d%c%d)%c(%d%c%d)", numbers[a], operands[rand() % 4], numbers[b], operands[rand() % 4], numbers[c], operands[rand() % 4], numbers[d], operands[rand() % 4], numbers[a], operands[rand() % 4], numbers[b], operands[rand() % 4], numbers[c], operands[rand() % 4], numbers[d]);

        if (strcmp(expr, solution) == 0) {
            return 1;
        }
    }

    printf("Invalid solution: cannot get 24 with these numbers.\n");
    return 0;
}

int solve(int *numbers, char *solution)
{
    int i, j, k, l, a, b, c, d, result;
    char operands[] = {'+', '-', '*', '/'};
    char expr[50];

    for (i = 0; i < 24; i++) {
        a = i / 6;
        b = i % 6 / 2;
        c = i % 2;
        d = 6 - a - b - c;

        sprintf(expr, "(%d%c%d)%c(%d%c%d)%c(%d%c%d)%c(%d%c%d)", numbers[a], operands[rand() % 4], numbers[b], operands[rand() % 4], numbers[c], operands[rand() % 4], numbers[d], operands[rand() % 4], numbers[a], operands[rand() % 4], numbers[b], operands[rand() % 4], numbers[c], operands[rand() % 4], numbers[d]);

        result = eval(expr);

        if (result == 24) {
            printf("Congratulations! You got 24 with these numbers!\n");
            printf("Solution: %s\n", expr);
            return 1;
        }
    }

    if (solution != NULL) {
        printf("Sorry, you cannot get 24 with these numbers.\n");
        printf("The correct solution is: %s\n", solution);
    }

    return 0;
}

int eval(char *expr)
{
    int i, j, k, l, a, b, c, d, result, temp;
    char operands[] = {'+', '-', '*', '/'};
    char op1, op2, *p;

    if (*expr == '(' && *(expr + strlen(expr) - 1) == ')') {
        p = expr + strlen(expr) - 2;
        while (*p != '(') {
            p--;
        }
        if (p == expr) {
            return eval(expr + 1);
        }
    }

    for (i = 0; i < strlen(expr); i++) {
        if (expr[i] == '(') {
            for (j = i + 1; j < strlen(expr); j++) {
                if (expr[j] == ')') {
                    temp = eval(expr + i + 1);
                    sprintf(expr + i, "%d", temp);
                    strcpy(expr + i + strlen(expr + i) + 1, expr + j + 1);
                    break;
                }
            }
        }
    }

    for (i = 0; i < 4; i++) {
        op1 = operands[i];
        for (j = 0; j < strlen(expr); j++) {
            if (expr[j] == op1) {
                for (k = j - 1; k >= 0; k--) {
                    if (isdigit(expr[k])) {
                        a = atoi(expr + k);
                    } else {
                        break;
                    }
                }
                for (k = j + 1; k < strlen(expr); k++) {
                    if (isdigit(expr[k])) {
                        b = atoi(expr + k);
                    } else {
                        break;
                    }
                }
                if (op1 == '+') {
                    result = a + b;
                } else if (op1 == '-') {
                    result = a - b;
                } else if (op1 == '*') {
                    result = a * b;
                } else if (op1 == '/') {
                    result = a / b;
                }
                sprintf(expr + k - strlen(expr), "%d", result);
                strcpy(expr + k - strlen(expr) + strlen(expr + k), expr + j + 1);
                j = 0;
            }
        }
    }

    return atoi(expr);
}

该程序使用了文件存储用户信息，用户登录和注册时需输入用户名和密码。程序会随机生成4个1到13之间的数字，并使用加减乘除（可带括号，先加减再乘除）计算是否能得到24。用户输入自己的算式，程序验证是否正确，如果得到24则提示正确并统计，否则提示错误并统计。用户可输入特殊符号表示无解，如果确实无解则提示正确并统计，否则提示有解并继续计算。用户可放弃有解计算，由程序提示正确答案并统计。程序会记录用户累计解正确次数、错误次数和放弃次数。