/*
Circular Shift Register

In digital circuits, a circular shift register is a construct similar to an array 
that can shift its contents left or right as if they are arranged in a circle. 
During a right shift, each element in the register is moved one space to the right, 
and the last element goes to the beginning of the register. Similarly, during a 
left shift, each element is moved to the left and the first element goes to the end.

For example, a shift register with the values [1,0,1,1,1,0] would behave as follows:


Right shift by 1: [0,1,0,1,1,1]
Right shift by 2: [1,0,1,0,1,1]
Right shift by 5: [0,1,1,1,0,1]

Left shift by 1:  [0,1,1,1,0,1]
Left shift by 3:  [1,1,0,1,0,1]


You must write a complete C program that models a circular shift register. 
Your program must read in the contents of the register and take in a shift 
direction and amount. It must then output the shifted contents of the register. 
You must define two functions that shift the register by 1 in the specified 
direction (one function for left and one for right shift). You must call the 
appropriate function repeatedly to shift the register by the specified amount.

HINT: The register will contain at most 1024 bits. Do not worry about error 
checking -- assume all inputs are correctly formatted.


====== SAMPLE RUN #1 ======
Enter the register size: 5
Enter the register contents: 1 1 0 1 0
Enter the shift direction [-1 for left, 1 for right]: 1
Enter the shift amount: 3

The contents of the shifted register are: 0 1 0 1 1
===========================

====== SAMPLE RUN #2 ======
Enter the register size: 10
Enter the register contents: 1 1 0 0 0 1 1 0 1 0   
Enter the shift direction [-1 for left, 1 for right]: -1
Enter the shift amount: 4387

The contents of the shifted register are: 0 1 0 1 1 0 0 0 1 1
===========================
*/

#include <stdio.h>
#include <stdlib.h>

void shiftRight(int reg[], int size){
	//Store the last value, move everything right, then put the temp value at the beginning
	int temp = reg[size - 1], i;
	for(i=size - 1; i > 0; i--){
		reg[i] = reg[i - 1];
	}
	reg[0] = temp;	
}

void shiftLeft(int reg[], int size){
	//Store the first value, move everything left, then put the temp value at the end
	int temp = reg[0], i;
	for(i=0; i < size - 1; i++){
		reg[i] = reg[i + 1];
	}
	reg[size - 1] = temp;		
}

int main(int argc, char *argv[]){
	int size, shiftdir, shiftamt, reg[1024], i;
	printf("Enter the register size: ");
	scanf("%d", &size);

	printf("Enter the register contents: ");
	for(i=0; i < size; i++){
		scanf("%d", &reg[i]);
	}

	printf("Enter the shift direction [-1 for left, 1 for right]: ");
	scanf("%d", &shiftdir);
	
	printf("Enter the shift amount: ");
	scanf("%d", &shiftamt);

	//Don't need to shift at all if it goes all the way around
	shiftamt %= size;

	//Left shift
	if(shiftdir < 0){
		for(i=0; i < shiftamt; i++){
			shiftLeft(reg, size);
		}
	}
	
	//Right shift
	else{
		for(i=0; i < shiftamt; i++){
			shiftRight(reg, size);
		}
	}

	printf("\nThe contents of the shifted register are:");
	for(i=0; i < size; i++){
		printf(" %d", reg[i]);
	}
	printf("\n");
	
	system("pause");
	return 0;
}