CareerCup1.2.cpp

CareerCup1.2.cpp

/* Chapter 1
 * 1.2 Implement function void reverse(char* str) in C or C++ which reverses a null-terminated string.
 */

#include <iostream>
#include <string>

using namespace std;

// Approach 1:
// Copy paste manipulation, not utilize the pointer in C++
// Doesn't change original string
void reverse_brute(char* str)
{
    int length = strlen(str);
    
    // check empty string
    if (length == 0) {
        cout << "The string length is 0" << endl;
        return;
    }
    
    char reverse_version[length+1];
    
    for (int i = 0; i < length; i++) {
        reverse_version[i] = str[length-1-i];
    }
    
    reverse_version[length] = '\0';
    
    cout << "Output from called function: " << reverse_version << endl;
}


// Approach 2:
// Utilize pointers to manipulate with string
// Swap char within string
void swap(char* a, char* b)
{
    char tmp[] = " ";
    *tmp = *a;
    *a   = *b;
    *b   = *tmp;
    
}

// My reverse implementation
void reverse(char* str)
{
    int length = strlen(str);
    
    if (length == 0) {
        cout << "The string length is 0" << endl;
        return;
    }
    
    int i = 0;
    
    while (i < length/2) {
        swap(str+i, str+length-1-i);
        i++;
    }
}

// The most elegant way to solve this problem
void reverse_elegant(char* str)
{
    char* begin = str;
    char* end   = str;
    // Move pointer end to the last non-terminal position
    while(*end != '\0'){
        end++;
    }
    end--;
    // No need to know length
    // Pointer manipulation within str
    while (begin < end ) {
        swap(begin, end);
        begin++;
        end--;
    }
    
}


int main()
{
    char test[] = "fdaDFAq4565$#&$5_5fdsllie";
    // char test2[] = "";  // For test empty string
    reverse_elegant(test);
    cout << test << endl;
}