创建非尾递归 function 的问题（c++ 新手）

Question

I've been working on solving this Reverse String and Non-Tail Recursion C++ problem. I've been able to write it successfully using libraries (STL, strlen) but need to be able to right it with just one int and one char in the function and no libraries.

This is what I'm aiming the code to look like but with the ReverseString function matching the specific restrictions.

#include <iostream>

using namespace std;

// constant
const int STRING_AMOUNT = 100;

// protocol
int ReverseString(char*);

// main method
int main() {
  char theString[STRING_AMOUNT] = "abcde";
  cout << "The string is: " << endl;
  cout << theString << endl << endl;
  cout << "Reversing the Function" << endl;
  ReverseString(theString);
  cout << "The string contains: " << endl;
  cout << theString << endl;
  // exit program
  return 0;
}

int ReverseString(char* reverseString) {

}

Answer 1

I'm thinking that we could use the int return value to find the length of the string.

For our base case, a string that is just the null terminator '\0' will always be zero.

if (*c == '\0') {
    return 0;
}

Starting from "abcde" , which has a null terminator appended at the end, we can't know for sure when the string will end. So we figure that the length of the string will always be 1 greater than the pointer, advanced one step ahead, which will make the char * point to "bcde" , as so on.

return 1 + StringReverse(c + 1);

And that's pretty much it for the recursive function.

int StringReverse(char *c) {
    if (*c == '\0') {
        return 0;
    }
    return 1 + StringReverse(c + 1);
}

Now this won't do anything on its own, the inner calls of the function won't know where the beginning of the string is to allow for swapping... except for the place that initially called it.

So we wrap the recursive function call with another function that performs the swapping.

void ReverseString(char *start) {
    int size = StringReverse(start);

    // The swap code goes here...
}