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Hey everyone, I've been working on an assignment for the past couple of days and while it is due tomorrow, I am very close to completing 
. While the assignment WAS due today, and I did have a method for the one I am stuck one, my professor had informed me half an hour before the assignment was due that he didn't want me to go about my method the way I had it, and had offered the class a day extension because everyone seemed to be stuck.
I've worked for the better part of the night on re-writing the multiplication method for this class and while it almost works I have found 2 pitfalls.
1. Multiplying two "BigInts" such as 2 x 40 will not yield 80, but 0, while 40 x 2 will yield 80. I've realized this is due to the size in the nested loop within multiply that increases the size of result, so when the number 2 enters to multiply 40, it will only increment size to 1 (rather then 2).
2. Multiplying two numbers such as 987 and 65 will yield 63,155 when the answer is 64,155. I haven't exactly narrowed this problem, but I think it has to do with the carry.
I'm not exactly asking for any specific coding changes, but I can't come up with anymore ideas, so any suggestions will be taking into mind.
The class:
The driver:
Thanks for all the help!
. While the assignment WAS due today, and I did have a method for the one I am stuck one, my professor had informed me half an hour before the assignment was due that he didn't want me to go about my method the way I had it, and had offered the class a day extension because everyone seemed to be stuck.I've worked for the better part of the night on re-writing the multiplication method for this class and while it almost works I have found 2 pitfalls.
1. Multiplying two "BigInts" such as 2 x 40 will not yield 80, but 0, while 40 x 2 will yield 80. I've realized this is due to the size in the nested loop within multiply that increases the size of result, so when the number 2 enters to multiply 40, it will only increment size to 1 (rather then 2).
2. Multiplying two numbers such as 987 and 65 will yield 63,155 when the answer is 64,155. I haven't exactly narrowed this problem, but I think it has to do with the carry.
I'm not exactly asking for any specific coding changes, but I can't come up with anymore ideas, so any suggestions will be taking into mind.
The class:
Code:
import java.lang.Math;
class BigInt {
private int digit[]; // represent the integer as an array of digits
private int size; // number of digits in the integer
private final int max = 50; // maximum number of digits in the integer
public BigInt() { // default constructor
digit = new int[max];
digit[0] = 0;
size = 1;
}
public BigInt(String num) { // constructor with initial String value
size = num.length();
digit = new int[max];
for (int ct = size - 1; ct >= 0; ct --) {
digit[ct] = Integer.parseInt(num.substring(size - ct - 1, size - ct));
}
}
public BigInt(int num) { // constructor with initial integer value
digit = new int[max];
int i = 0;
size = 0;
do {
digit[i] = num % 10;
num = num / 10;
i++;
size++;
}while(num > 0);
}
public BigInt(BigInt num) {
int i = 0;
this.size = num.size;
digit = new int[max];
for(i = 0; i < num.size; i++) {
this.digit[i] = num.digit[i];
}
}
public String toString() { // override Objectís version
String intString = "";
for (int ct = size - 1; ct >= 0; ct --) {
intString = intString + String.valueOf(digit[ct]);
}
return intString;
}
public int compareTo(BigInt other) {
int compare = 0; //variable to store the return value after both objects are compared
if(this.size > other.getSize()) { // return 1 if this greater than other
compare = 1;
}else if(this.size < other.getSize()) { // return -1 if this is less than other
compare = -1;
}else if(this.size == other.getSize()) { // return 0 if both are equal
//int i = size-1;
int cnt = 0;
int othercnt = 0;
for(int i = size-1; i >= 0; i--) {
if(this.digit[i] > other.digit[i]) {
cnt++;
}
else if(this.digit[i] < other.digit[i]) {
othercnt++;
}
}
if(cnt > othercnt)
compare = 1;
else if (cnt < othercnt)
compare = -1;
else
compare = 0;
}
return compare;
}
/* [0][5][2]
[5][5][3]
*/
public BigInt plus(BigInt arg) { // add two BigIntís
BigInt sum = new BigInt();
int carry = 0;
if(this.size > arg.getSize()) {
sum.size = this.size;
for(int i = 0; i < this.size; i++) {
sum.digit[i] = ((this.digit[i] + arg.digit[i] + carry) % 10); //take out the smaller digit of the two
carry = (this.digit[i] + arg.digit[i] + carry) / 10; //carry overthe extra
//System.out.println("carry " + carry);
}
} else if(this.size < arg.getSize()) {
sum.size = arg.size;
for(int i = 0; i < arg.size; i++) {
sum.digit[i] = ((this.digit[i] + arg.digit[i] + carry) % 10); //take out the smaller digit of the two
carry = (this.digit[i] + arg.digit[i] + carry) / 10; //carry overthe extra
//System.out.println("carry " + carry);
}
} else { //if(this.size == arg.getSize()) {
sum.size = this.size;
for(int i = 0; i < this.size; i++) {
sum.digit[i] = (this.digit[i] + arg.digit[i] + carry) % 10;
carry = (this.digit[i] + arg.digit[i]) / 10;
//System.out.println("carry " + carry);
//System.out.println(sum.size);
}
}
if(carry > 0) {
//sum.size++;
sum.digit[sum.size] = carry;
sum.size++;
}
return sum;
}
public BigInt times(BigInt other) { //multiply two BigInts
BigInt result = new BigInt();
BigInt product = new BigInt();
// product.size = 0;
int carry = 0;
//if(this.size > other.size) {
result.size = 0; //set size of the result to 0, original would be set to 1
for(int i = 0; i < other.size; i++) {
carry = 0; //make sure the carry is 0 before it enters the loop for the second iteration
if(i > 0) {
for(int k = 0; k <= i; k++)
result.digit[i-k] = 0;
}
for(int j = 0; j < this.size; j++) {
if(i == 0) { //only increments size the first time through the iteration of the loop
result.size++;
System.out.println("size " + result.size);
}
if(i > 0) {
result.digit[i+j] = ((other.digit[i] * this.digit[j]) + carry) % 10; //mulitply operation
carry = (other.digit[i] * this.digit[j]) / 10; // carry for the digits
} else {
result.digit[j] = ((other.digit[i] * this.digit[j]) + carry) % 10; //mulitply operation
carry = (other.digit[i] * this.digit[j]) / 10; // carry for the digits
}
if(j == this.size-1 && carry > 0) { //if a carry remains and all the mulitplication has been done
result.digit[result.size] = carry; //set the last digit to the carry
result.size++;
}
}
for(int j = result.size; j >= 0; j--) {
System.out.print(result.digit[j]);
}
System.out.println();
product = product.plus(result);
}
// }
// product = product.plus(result);
return product;
}
public int getSize() {
return this.size;
}
}The driver:
Code:
import java.io.*; // for BufferedReader
public class BigIntSimpleTest {
public static void main(String[] args) throws IOException {
BigInt num, num1, num2 = new BigInt("1");
BigInt zero = new BigInt();
BufferedReader stdin = new BufferedReader(
new InputStreamReader(System.in));
//System.out.println(10 % 10);
System.out.println("First BigInt: " + new BigInt(234));
System.out.println("Next BigInt: " + new BigInt("5678"));
while (num2.compareTo(zero) != 0) {
System.out.print("A big integer: ");
num = new BigInt(stdin.readLine());
System.out.println(num);
System.out.print("Another big integer: ");
num1 = new BigInt(stdin.readLine());
System.out.println(num1);
if (num.compareTo(num1) == 1) {
System.out.println(num + " is bigger.");
}
else if (num.compareTo(num1) == -1) {
System.out.println(num1 + " is bigger.");
}
else {
System.out.println(" They are both " + num);
}
num2 = num1.plus(num);
System.out.println("The sum is: " + num2);
num2 = num.times(num1);
System.out.println("The product is: " + num2);
}
}
}Thanks for all the help!