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@jianminchen
Created February 6, 2018 19:49
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Float number and operators to get maximum number, brute force solution. I had a good time to play the code, and it works; but I am not sure how it is designed from line 43 to line 67
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace floatNumberAndOperators
{
class Program
{
static void Main(string[] args)
{
var maximum = EvaluateMaximize(new double[] { 1, 12, -3 });
}
/// <summary>
/// Float numbers and operators: +, -, *, /
/// What is the maximum number?
/// code review Feb. 6, 2018
/// [1, 12, -3], 33, first two numbers 1 - 12 = -11
/// This function is a brute force solution.
/// </summary>
/// <param name="terms"></param>
/// <returns></returns>
public static double EvaluateMaximize(double[] terms)
{
int N = terms.Length;
if (N > 16)
{
throw new ArgumentException("Too complex for this solution");
}
var intermediate = new double[1 << (2 * N)];
int iInterm = 0;
double maximized = 0;
intermediate[iInterm++] = terms[0]; // 1
for (int index = 1; index < N; index++)
{
int iMaxInterm = iInterm - 1;
double m = 0;
for (int iPrev = iMaxInterm; iPrev >= 0; iPrev--)
{
double prev = intermediate[iPrev];
var startIndex = iPrev * 4;
var current = terms[index];
intermediate[startIndex + 0] = prev * current;
intermediate[startIndex + 1] = prev / current;
intermediate[startIndex + 2] = prev - current;
intermediate[startIndex + 3] = prev + current;
if (index != N - 1) // skip if not the last term
continue;
m = Math.Max(m, intermediate[startIndex + 3]);
m = Math.Max(m, intermediate[startIndex + 2]);
m = Math.Max(m, intermediate[startIndex + 1]);
m = Math.Max(m, intermediate[startIndex + 0]);
}
maximized = m;
iInterm *= 4;
}
return maximized;
}
}
}
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