C语言记忆游戏程序在序列长度增至5位时出现运行时错误

问题描述 #

编写的Simple Simon记忆游戏初始3位序列运行正常，但当序列长度增至5位时，对比用户输入数组guessedNumArr与目标数组numToGuess时，numToGuess[0]的值会被莫名修改，导致玩家直接失败。游戏规则为：电脑短时间显示数字序列，玩家记忆后输入相同序列，连续3次成功则序列长度增加，目标是尽可能延续游戏。

核心错误分析 #

1. 变长数组(VLA)的误用：
   代码中numToGuess[difficulty]和guessedNumArr[difficulty]是变长数组，在main函数开头声明时difficulty的值为5，后续difficulty增加后，数组实际长度仍为5，当访问索引超过4的元素时，会发生栈内存越界，破坏相邻变量（包括numToGuess[0]）的值。

2. scanf格式符不匹配导致栈溢出：
   处理用户输入Y/N时使用scanf("%s", &Y_N)，但Y_N是单个char类型，%s会读取字符串并写入终止符\0，这会超出Y_N的内存空间，覆盖栈中其他变量（如numToGuess的元素）。

3. 随机数种子重复初始化：
   srand(time(NULL))放在循环内部，每次循环都会重置随机数种子。由于time(NULL)返回秒级时间，短时间内多次循环会导致生成相同的随机序列，同时也可能影响程序执行时序，间接引发内存问题。

修复方案 #

• 改用动态内存分配：使用malloc和realloc根据当前difficulty动态调整数组大小，避免越界。
• 修正scanf格式符：对单个字符输入使用%c，并通过getchar()处理输入缓冲区的换行符，避免残留字符干扰后续输入。
• 初始化随机数种子一次：将srand(time(NULL))移到main函数开头，仅初始化一次。
• 移除goto语句：用循环结构替代goto，提升代码可读性和可维护性。

完整修正代码 #

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

int main() {
    bool play = true;
    time_t now;
    int try_count = 1, anotherGame;
    int difficulty = 3;  // 初始难度改为3，符合游戏描述
    int *numToGuess = malloc(difficulty * sizeof(int));
    int *guessedNumArr = malloc(difficulty * sizeof(int));
    int count = 0, guessedNum, singleScore = 0, totalScore = 0;

    if (!numToGuess || !guessedNumArr) {
        printf("内存分配失败\n");
        return 1;
    }

    // 仅初始化一次随机数种子
    srand(time(NULL));

    puts("\nSimple Simon is a memory-test game. In this game, the\n"
         "computer displays a sequence of digits on the screen for a short period of time.\n"
         "You then have to memorize them, and when the digits disappear from the screen,\n"
         "you must enter exactly the same sequence of digits. "
         "Each time you succeed 3 times in a row, the process repeats with a longer sequence of digits for you to try.\n"
         "The objective is to continue the process for as long as possible\n"
         "Press enter to play");
    // 处理换行符
    getchar();

    do {
        int consecutive_success = 0;
        while (consecutive_success < 3) {
            const unsigned int DELAY = 2;

            // 生成目标序列
            for (int i = 0; i < difficulty; i++) {
                numToGuess[i] = rand() % 10;
                printf("%d   ", numToGuess[i]);
            }

            // 延迟后清空屏幕（用换行替代，实际可根据系统调用清屏命令）
            now = clock();
            while (clock() - now < DELAY * CLOCKS_PER_SEC);
            puts("\n\n");

            // 获取玩家输入
            puts("Try to enter the same exact sequence of numbers, remember to put a space in between the numbers:\n");
            for (int k = 0; k < difficulty; k++) {
                scanf("%d", &guessedNum);
                guessedNumArr[k] = guessedNum;
            }
            // 清除输入缓冲区的换行符
            while (getchar() != '\n');

            // 对比输入与目标序列
            count = 0;
            for (int j = 0; j < difficulty; j++) {
                printf("%d --- %d\n", guessedNumArr[j], numToGuess[j]);
                if (guessedNumArr[j] == numToGuess[j]) {
                    count++;
                }
            }
            try_count++;

            if (count == difficulty) {
                consecutive_success++;
                totalScore++;
                printf("正确！已连续成功%d次\n", consecutive_success);
            } else {
                char Y_N;
                printf("抱歉，你输了。总得分：%d。是否再玩一次？Y/N\n", totalScore);
                while (true) {
                    scanf(" %c", &Y_N);  // 空格跳过空白字符
                    Y_N = tolower(Y_N);
                    if (Y_N == 'y') {
                        try_count = 0;
                        totalScore = 0;
                        consecutive_success = 0;
                        difficulty = 3;
                        // 重新分配初始难度的内存
                        numToGuess = realloc(numToGuess, difficulty * sizeof(int));
                        guessedNumArr = realloc(guessedNumArr, difficulty * sizeof(int));
                        if (!numToGuess || !guessedNumArr) {
                            printf("内存分配失败\n");
                            return 1;
                        }
                        break;
                    } else if (Y_N == 'n') {
                        printf("游戏结束\n");
                        play = false;
                        break;
                    } else {
                        printf("请输入Y或N\n");
                    }
                }
                if (!play) break;
            }
        }

        if (!play) break;

        // 连续成功3次，询问是否继续
        int gotItwrong = 0;
        char yOrN;
        while (true) {
            if (gotItwrong == 0) {
                puts("已连续成功3次，输入Y继续（序列长度+1），输入N结束游戏\n");
            }
            scanf(" %c", &yOrN);
            yOrN = tolower(yOrN);
            if (yOrN == 'y') {
                difficulty++;
                // 重新分配内存
                numToGuess = realloc(numToGuess, difficulty * sizeof(int));
                guessedNumArr = realloc(guessedNumArr, difficulty * sizeof(int));
                if (!numToGuess || !guessedNumArr) {
                    printf("内存分配失败\n");
                    return 1;
                }
                consecutive_success = 0;
                break;
            } else if (yOrN == 'n') {
                printf("游戏结束，总得分：%d\n", totalScore);
                play = false;
                break;
            } else {
                printf("请输入Y或N\n");
                gotItwrong++;
            }
        }

    } while (play == true);

    // 释放动态分配的内存
    free(numToGuess);
    free(guessedNumArr);

    return 0;
}

内容的提问来源于stack exchange，提问作者Giacomo D.G.