Question

我正在尝试从C数组中复制一个特定的单词并将其放入另一个c数组中，以便稍后可以显示输出，但是当我执行该程序时，第一个函数调用起作用了（（输出/终端） “复制\“光亮\”，应显示\“光亮\”。\ n“; 但是，当我再次调用该函数时，它给我的结果（输出/端子）是超级的，而不是超级的（因为我在参数中指定了，我想复制前五个字符）。怎么了？

#include <iostream>
#include <cstring>
#include <cctype>
#include <stdio.h>
#include <string.h>
#include <algorithm> 

using std::cin;
using std::cout;
using std::endl;

// function declarations
char* copy(char* destination, const char* source, size_t num);


int main()
   {
   const int WORDSIZE = 15;
   char words[][WORDSIZE] = {"sprightful", "reason to row", "New York", "Bolton", "Frida", ""};
   char word[WORDSIZE];



   copy(word, words[0], sizeof(word) - 1);
   cout << word << endl << endl;



   copy(word, "Supercalifragilisticexpialidocious", 5);
   cout << word << endl << endl;

   return 0;
    }


char* copy(char* destination, const char* source, size_t num)
 {
    strncpy(destination, source, num); 
    return destination;
 }

Answer 1

您不会在两个函数调用之间清除word。在第二次通话中，它只会覆盖前5个字符（“超级”），其余的是您上一次通话的结果。

Answer 2

@Brandon是正确的。尝试在函数调用之间清除单词：

    int main()
    {
    const int WORDSIZE = 15;
    char words[][WORDSIZE] = { "sprightful", "reason to row", "New York", "Bolton", "Frida", "" };
    char word[WORDSIZE];


    // Test the copy function
    std::cout << "Copy \"sprightful\", should see \"sprightful\".\n";
    copy(word, words[0], sizeof(word) - 1);
    cout << word << endl << endl;

    memset(&word[0], 0, sizeof(word)); //Clear the char array.

    // Test the limit on the copy function
    cout << "Copy \"Supercalifragilisticexpialidocious\", should see \"Super\".\n";
    copy(word, "Supercalifragilisticexpialidocious", 5);
    cout << word << endl << endl;

    getchar();
    return 0;
}

我没有得到正确的输出

2 个答案: