Xcode每次运行C++测试都会给出不同的结果

Question

我正在接收一个char数组的程序。在那个char数组中，数字是用空格分隔的。该程序应该收到一个号码并将该号码的回文号码添加到自己。如果结果不是回文，那么我们应该将结果的回文结果添加到结果中，等等，直到结果为回文。例如，如果char数组是“195”，那么195 + 591 = 786. 786不是回文，所以786 + 687 = 1473。1473 + 3741 = 5214。最后5214 + 4125 = 9339，这是一个回文，所以这是答案。然后，程序应该返回它运行的答案的数量，然后回答答案。在这个例子中，程序将返回“4 9339”。

我的程序工作（据我所知），但无论什么原因，每当我运行Xcode时，它会返回不同的结果。例如，有一次我运行它，除了情况7以外，一切都很好。下次运行它时，每个测试都失败了。如果我再次运行它，除7和9之外，每个案例都可以工作。有人知道为什么会发生这种情况吗？以下是我的所有代码，包括Xcode运行的测试用例。我也尝试评论该计划中发生的事情。

我将不胜感激任何人的帮助！当谈到C++时，我是一个业余爱好者，所以它可能是我忽略的一些微不足道的东西，也可能是更先进的东西 - 我真的不确定。提前感谢大家！

编辑：我使用Xcode的调试器，没有任何失败或看起来不合适，当我这样做，这使得它只有更神秘的为什么它失败时，我没有调试运行测试。编辑2：然后测试案例由我的教授提供，而不是我自己。

#include <iostream> 
#include <string> 
using namespace std; 

//returns the reverse of a number 
unsigned long reverse(unsigned long n) { 
    unsigned long reverse = 0; 

    while(n != 0) { 
     unsigned long remainder = n%10; 
     reverse = reverse*10 + remainder; 
     n /= 10; 
    } 

    return reverse; 
} 

//return what the palindrome result is 
string palindrome(string numberInString, int &counter) { 
    counter++; 
    //convert input, which is a string, to int 
    unsigned long number = std::stol(numberInString); 
    //reverse number and assign it to numberReversed 
    unsigned long numberReversed = reverse(number); 
    //add the number and its reverse 
    unsigned long result = number + numberReversed; 
    //reverse the result and assign it to resultReversed 
    unsigned long resultReversed = reverse(result); 
    //check to see if result and its reverse are equal; otherwise, keep going until they are 
    while (result != resultReversed) { 
     counter++; 
     //reassign number as result 
     number = result; 
     //reverse number and assign it to numberReversed 
     numberReversed = reverse(number); 
     //add the number and its reverse 
     result = number + numberReversed; 
     //reverse the result and assign it to resultReversed 
     resultReversed = reverse(result); 
    } 

    //return result 
    return std::to_string(result); 
} 

//the "main" method 
char* find(const char* array) { 
    //instatntite counter, which will be used later 
    int counter = 0; 
    //instantiate result string, which is what we are returning 
    string result = ""; 
    int i = 0; 
    //will be used to construct int being checked as a palindrome 
    string currentNumberConstruction = ""; 
    //go through array until end of array 
    while (array[i] != '\0') { 
     //if find a space 
     if (array[i] == ' ') { 
      //call palindrome function and add it to result later on 
      string palindromeNumber = palindrome(currentNumberConstruction, counter); 
      result += std::to_string(counter); 
      //add to result how many cycles until palindrome found 
      result += " " + palindromeNumber + " "; 
      //reset counter (how many cycles until palindrome found) 
      counter = 0; 
      //reset currentNumberConstruction (int being checked as a palindrome) 
      currentNumberConstruction = ""; 
      //continue through array 
      i++; 
     } else { 
      //add char checked to currentNumberConstruction (int being checked as a palindrome) 
      currentNumberConstruction += array[i]; 
      //continue through array 
      i++; 
     } 
    } 

    if (currentNumberConstruction != "") { 
     string palindromeNumber = palindrome(currentNumberConstruction, counter); 
     result += std::to_string(counter); 
     result += " " + palindromeNumber; 
     counter = 0; 
     currentNumberConstruction = ""; 
     i++; 
    } 

    //convert result from string to char* 
    char* realResult = new char[result.length()]; 
    for (unsigned int j = 0; j < result.length(); j++) { 
     realResult[j] = result[j]; 
    } 

    //return char* realResult 
    return realResult; 
} 

int main() { 
    const char* array = NULL; 
    const char* expected = 0; 

    for (int i = 0; i < 10; i++) { 
     switch (i) { 
      case 0: 
       array = "195 265 750"; 
       expected = "4 9339 5 45254 3 6666"; 
       break; 
      case 1: 
       array = "2 99 4000000000 20 100 1"; 
       expected = "1 4 6 79497 1 4000000004 1 22 1 101 1 2"; 
       break; 
      case 2: 
       array = "79 88 97 99"; 
       expected = "6 44044 6 44044 6 44044 6 79497"; 
       break; 
      case 3: 
       array = "157 158 166 167 175 188 193 197"; 
       expected = "3 8888 3 11011 5 45254 11 88555588 4 9559 7 233332 8 233332 7 881188"; 
       break; 
      case 4: 
       array = "266 273 274 292 365"; 
       expected = "11 88555588 4 5115 4 9559 8 233332 11 88555588"; 
       break; 
      case 5: 
       array = "1089 1091 1099"; 
       expected = "4 79497 1 2992 2 11011"; 
       break; 
      case 6: 
       array = "19991 2914560 12345678"; 
       expected = "8 16699661 5 47977974 1 99999999"; 
       break; 
      case 7: 
       array = "777"; 
       expected = "4 23232"; 
       break; 
      case 8: 
       array = "130031 9"; 
       expected = "1 260062 2 99"; 
       break; 
      case 9: 
       array = "123456789"; 
       expected = "2 12222222211222222221"; 
       break; 
      default: 
       cout << "we should never get here" << endl; 
       return -1; 
     } 
     char* actual = find(array); 
     bool equal = strcmp(expected, actual) == 0; 
     cout << "test " << (i + 1) << ": " << (equal ? "ok" : "failed"); 
     if (!equal) { 
      cout << " expected [" << expected << "] but was [" << actual << "]"; 
     } 
     cout << endl; 

     delete actual; 
    } 
    return EXIT_SUCCESS; 
} 

Answer 1

你的问题是在这里：

char* array = NULL; 

其实你不分配任何内存来存储阵列，你需要，给它一些内存的方式来初始化此。否则，你只是在系统中选择随机存储器，最终你可能会得到一个SegFault。 这可能就像这样：

char array[100]; 

或者你可以使用的std :: string代替。这会创建一个包含100个字符的字符数组，您可以根据需要调整大小。

Answer 2

不知道它是唯一的错误，但你不空终止结果：

char* realResult = new char[result.length()]; 

应该是：

char* realResult = new char[result.length()+1]; 
realResult [result.length()] = 0; 

否则的行为可能是很随机的。