The code is to shift a binary number to a certain amount of shifts. It gives a result of the number shifted to the left and the right. However, when I run the code, it doesn't shift to the left properly. For example, if I want 2 shifts for 100 it gives 000 instead of 010, and asking for 3 or more shifts doesn't work. And shifting 12345 by 2 gives 34555 instead of 34512. The shift to the right works fine, but shifting to the left isn't working. How do I fix it?

 #include <cstring>
 #include <iostream>

using namespace std;

void shiftCstring(char pstrMsg[]);
void initCString(char pstrMsg[], int pSize);
void shiftCstring2(char pstrMsg[], int numberOfBits);

void initCString2 (char pstrMsg[], int pSize);
void shiftCstring3(char pstrMsg[]);
void shiftCstring4(char pstrMsg[], int numberOfBits);

int main()
{
    char cstrBin1[9];
    cout << "Enter 8-bit binary number: ";
    cin.getline(cstrBin1, 9);
    char cstrBin2[17];
    char cstrBin3[17];
    initCString(cstrBin2, 16);
    strcpy(cstrBin2, cstrBin1);
    cstrBin2[9] = '0';
    initCString2(cstrBin3, 16);
    strcpy(cstrBin3, cstrBin1);
    cstrBin3[9] = '0';
    int shifted;
    cout << "How many times do you want to shift? ";
    cin >> shifted;
    if (shifted == 1) {
        shiftCstring3(cstrBin3);
        shiftCstring(cstrBin2); 
        cout << "After one shift right: "<<cstrBin2 << endl;
        cout << "After one shift left: "<<cstrBin3 << endl;
    } else if (shifted > 1) {
        shiftCstring3(cstrBin3);
        shiftCstring4(cstrBin3, (shifted-1));
        shiftCstring(cstrBin2);
        shiftCstring2(cstrBin2, (shifted-1));
        cout << "After " << shifted << " shifts right: "<< cstrBin2 << endl;
        cout << "After " << shifted << " shifts left: "<< cstrBin3 << endl;
    } else {
        cout << "Not a valid number of shifts." << endl;
    }

    return 0;
}

void initCString(char pstrMsg[], int pSize)
{
    for (int i=0;i<pSize;i  ) {
        pstrMsg[i] = pstrMsg[i 1];
    }
}
void shiftCstring(char pstrMsg[])
{
    char tmp = pstrMsg[strlen(pstrMsg)-1];
    for (int i=(strlen(pstrMsg)-1);i>0;i--) {
    pstrMsg[i]=pstrMsg[i-1];
    }
    pstrMsg[0]=tmp;
}

void shiftCstring2(char pstrMsg[], int numberOfBits)
{
    while (numberOfBits>0) {
        shiftCstring(pstrMsg);
        numberOfBits--;
    }
}
void initCString2 (char pstrMsg[], int pSize)
{
    for (int i=pSize;i>0;i--) {
        pstrMsg[i] = pstrMsg[i-1];
    }
}
void shiftCstring3(char pstrMsg[])
{
    char tmp = pstrMsg[strlen(pstrMsg) 1];
    for (int i=0; i<(strlen(pstrMsg)-1);i  ) {
        pstrMsg[i] = pstrMsg[i 1];
    }
    pstrMsg[0] = tmp;
}
void shiftCstring4(char pstrMsg[], int numberOfBits) {
    while (numberOfBits>0) {
        shiftCstring3(pstrMsg);
        numberOfBits--;
    }
}

CodePudding user response：

Here's shiftCstring3 fixed.

void shiftCstring3(char pstrMsg[])
{
    size_t len = strlen(pstrMsg);
    if (len == 0)
        return;
    char tmp = pstrMsg[0];
    for (size_t i = 0; i < len - 1;   i)
        pstrMsg[i] = pstrMsg[i   1];
    pstrMsg[len - 1] = tmp;
}

As indicated above you have many other problems in your code.

CodePudding user response：

How do I fix it?

First fix your problem description. You are trying to rotate a string, not shift it.

Then forget about C and learn C : use std::string

Rotating by N left or right is a simple call to std::rotate. (Thanks Paul).