CareerCup

// Return value overflows for large x and x ~ 0
double Square(double x) {
  return x / (1.0 / x);
}

Add original number the same num of times as the value of orig. Num. So square of 6 will be adding 6, 6 times.

for (int i=0 ;i<n; i++)
  square+=n;

every number can be written as a sum of 2s and 1.
like 5 = 2+2+1, 6 = 2+2+2
So 5*5 = 5*(2+2+1) = 5*2 + 5*2 + 5
Use left shift for *2 as asterisk is not allowed. then add num for odd.

<pre lang="java" line="1" title="CodeMonkey28074" class="run-this">public class BitwiseSquare {

/**
* Simple multiplication using bitwise operators.
*/
public static int multiply(int a, int b) {
int product = 0;

while (a > 0) {
if ((a & 1) != 0)
product += b;
b = b << 1;
a = a >> 1;
}
return product;
}

/**
* This is better explained using an example. Example: 24 = 16+8 (bit 4th
* and 3rd) 24^2 = (16+8)^2 = 16^2 + 8^2 + 2x16x8 26^2 = (16+8+2)^2, using
* powers of 2. (16+8+2)^2 = 2*2+2 + 8*8+2*8*(2) + 16*16+2*16*(2+8) = 676
*/
public static int square(int a) {
int bitpos = 0;
int result0 = 0; // 16*16 + 8*8 + 2*2
int result1 = 0; // 2 + 2*8*(2) + 2x16x(2+8)
int temp = 0; // 2+8+16

while (a > 0) {
if ((a & 1) != 0) {
// 16^2 = (2^4)^2 = 2^(4+4)
int b = 1;
// b = 16 = 2^4
b = b << bitpos;
// result1 += 2 * b * temp;
result1 += multiply(b, temp) << 1;
temp += b;

// b = 16^2 = 2^(4+4)
b = b << bitpos;
result0 += b;
}
a = a >> 1;
bitpos++;
}

return result0 + result1;
}

public static void main(String[] args) throws java.lang.Exception {
for (String s : args) {
int val = Integer.parseInt(s);
System.out.println(val + "^2 = " + square(val));
}
}
}
</pre><pre title="CodeMonkey28074" input="yes">1 3 26</pre>

another solution:

Use the fact that (n-1)^2 = n^2 -2n + 1 and use recursion

{
int square(int n)
{
  if(n == 1 || n == 0) return n;
  if(n < 0) return square(-n);

  return square(n-1)+n+(n-1);
}

original question states a number not an int, how about doubles?

What the heck is a carrot sign?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
int result;
result = sqrtnum(100);
Console.WriteLine("The value is " + result);
Console.Read();

}
public static int sqrtnum(int num)
{
int total = 0;
int count = num;
List<int> l = new List<int>();
for (int i = -1; i < count; i++)
{
l.Add(num);
Console.WriteLine(l.ToString());
}


for (int j = 0; j < l.Count - 1; j++)
total += l[j];
return total ;
}

}
}

(int)square:id
{
int a;
a=id;
for(int i=0;i<a;i++)
a=a+a;
return a;
}

public int square(int a, int b) {
if (b==1) return a;
return a+square(a,b-1);
}

A lot of answers are focusing on integer numbers only. I don't think it states anywhere that we should limit the function to integer numbers.

if we're allowed to use <math.h> you can do:

double square(double x) {
	return exp(log(x) + log(x));
}

a^b = exp(b*log(a))