c++ - 为考试而死记硬背——我错过了什么(C++ 字符串操作)

Question

用一些示例问题(我没有解决方案)在字符串操作上为 C++ 考试做准备 - 下面是今天的手工作业。尽管它工作正常 - 如果您遇到任何明显的失误/更好的做事方式，那就太棒了，请给我一个简短的说明，我需要快速学习一些 C++ :)

谢谢!

#include <iostream>
#include <cctype>
#include <cstring>

//#include "words.h"

using namespace std;

void reverse(const char un_rev[], char rev[]);
void clean(const char in_string[], char out_string[]);
//produces 'cleaned' copy of the string and passes on to recursive compare
bool compare(const char input_1[], const char input_2[]);
//the recursive bit
bool compare_recur(char input_1[], char input_2[]);
bool palindrome(const char input[]);
//no mixed capps for func below!
int min_pos(int starting_pos, char input[]);
void sort(char input[]);
bool anagram(const char input_1[], const char input_2[]);



int main() {

  /*** QUESTION 1 ***/
  char reversed[9];
  reverse("lairepmi", reversed);
  cout << "'lairepmi' reversed is '" << reversed << "'" << endl;
  reverse("desserts", reversed);
  cout << "'desserts' reversed is '" << reversed << "'" << endl << endl;


  /*** QUESTION 2 **/
  cout << "The strings 'this, and THAT......' and 'THIS and THAT!!!' are ";
  if (!compare("this, and THAT......", "THIS and THAT!!!"))
    cout << "NOT ";
  cout << "the same" << endl << "  (ignoring punctuation and case)" << endl;

  cout << "The strings 'this, and THAT' and 'THIS, but not that' are ";
  if (!compare("this, and THAT", "THIS, but not that")) 
    cout << "NOT ";
  cout << "the same" << endl << "  (ignoring punctuation and case)" << endl << endl;

  /*** QUESTION 3 **/

  cout << "The string 'rotor' is ";
  if (!palindrome("rotor"))
    cout << "NOT ";
  cout << "a palindrome." << endl;

  cout << "The string 'Madam I'm adam' is ";
  if (!palindrome("Madam I'm adam"))
    cout << "NOT ";
  cout << "a palindrome." << endl;
  cout << "The string 'Madam I'm not adam' is ";
  if (!palindrome("Madam I'm not adam"))
    cout << "NOT ";
  cout << "a palindrome." << endl << endl;

  /*** QUESTION 4 **/

  cout << "The string 'I am a weakish speller!' is ";
  if (!anagram("I am a weakish speller!", "William Shakespeare"))
    cout << "NOT ";
  cout << "an anagram of 'William Shakespeare'" << endl;

  cout << "The string 'I am a good speller!' is ";
  if (!anagram("I am a good speller!", "William Shakespeare"))
    cout << "NOT ";
  cout << "an anagram of 'William Shakespeare'" << endl;

  return 0;
}



void reverse(const char* un_rev, char rev[]) {

  int len = 0;
  len = strlen(un_rev);
  int i = 0;

  rev[len+1] = '\0'; //null terminate string

  while (len >= 0) {
    rev[i] = un_rev[len -1];
    i++;
    len--;
  } 
}

void clean(const char in_string[], char out_string[]) {
  int n =0;

  for (int i = 0; in_string[i]; i++) {

    if (isalpha(in_string[i])) {
      out_string[n] = toupper(in_string[i]);
      n++;
    }
  }
  out_string[n] = '\0';
  //  cout << "out: " << out_string;
}


bool compare(const char input_1[], const char input_2[]) {

  //cleaned copies of string
  int len1 = strlen(input_1);
  int len2 = strlen(input_2);

  char cinput_1[len1+1];
  cinput_1[len1+1] = '\0';
  char cinput_2[len2+1];
  cinput_2[len2+1] = '\0';

  clean(input_1, cinput_1);
  clean(input_2, cinput_2);

  return(compare_recur(cinput_1, cinput_2));

}

//recursive bit of the compare function
//possibly work into a single func?
bool compare_recur(char input_1[], char input_2[]) {

  if (!(*input_1) || !(*input_2)) {
    return true;
  } else if ( *input_1 != *input_2) {
    return false;
  }

  return compare_recur(++input_1, ++input_2);

}


bool palindrome(const char input[]) {

  int len = strlen(input);

  char cinput[len+1];
  cinput[len+1] = '\0';

  reverse(input, cinput);
  compare(input, cinput);

}


int min_pos(int starting_pos, char input[]) {
  int min = starting_pos;
  char min_char = input[starting_pos];

  for (int i = starting_pos; input[i]; i++) {

    if (input[i] < min_char) {
      min = i;
      min_char = input[i];
    }
  }
  return min;
}


void sort(char input[]) {
  char temp;
  int the_min = 0;

  for(int i = 0; input[i]; i++) {
    the_min = min_pos(i, input);

    if ((the_min) != i) { 
      //swap
      temp = input[the_min];
      input[the_min] = input[i];
      input[i] = temp;

    }

  }
}


bool anagram(const char input_1[], const char input_2[]) {

  int len1 = strlen(input_1);
  int len2 = strlen(input_2);

  char cinput_1[len1+1];
  cinput_1[len1+1] = '\0';
  char cinput_2[len2+1];
  cinput_2[len2+1] = '\0';

  clean(input_1, cinput_1);
  clean(input_2, cinput_2);

  sort(cinput_1);
  sort(cinput_2);

  return compare(cinput_1, cinput_2);  

}

Answer 1

正如人们所说，使用 std::string 将使事情变得更加简单和安全。如果您必须使用 C 风格的字符串，这里是对您的代码的一些批评:

---

1.在许多地方，您的代码等同于

buf[len+1] = '\0';

应该是

buf[len] = '\0';

---

2。 palindrome函数不返回值。

---

3。此代码(其变体出现在多个地方)不是标准 C++，因为数组大小不是常量:

char cinput[len+1];

对于可变大小的数组，你需要动态分配它们:

char *cinput = new char[len+1];
//... use the array ...
delete[] cinput;

当然，std::string甚至 std::vector<char>将使这里的事情变得更容易。