For example, if coins = [1, 2, 5] and N = 11, return true if coins = [3, 77] and N = 100, return - objective-c

Question

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Given a number of coins with different denominations, e.g. [1, 2, 5] and test if they could be used to make up a certain amount (N), assuming you can use unlimited number of coins in each denomination. For example, if coins = [1, 2, 5] and N = 11, return true if coins = [3, 77] and N = 100, return

Answer 1

The idea is use a recursive function (here it will calculate with one first coin vs array of other coins then recursively reduce size of coin array ).
But sr I'm not familiar with Objective-C so I write one using C#. Use should convert it to Objective-C.
bool CanDo(int n, int [] arr)
{
if (arr.Length == 1)
{
if (n % arr[0] == 0)
{
return true;
}
}
else
{
var ls = new List<int>(arr);
ls.RemoveAt(0);
int [] newarr = ls.ToArray(); //Create New array by deleting first element(current calculated element) of old array
for(int i = 0; i <= n/arr[0]; i++)
{
int next_n = n - i * arr[0];
if (next_n == 0)
{
return true;
}
else if (next_n < 0)
{
break;
}
else if(next_n > 0)
{
if( CanDo(next_n, newarr) )
{
return true;
}
}
}
}
return false;
}
This is full code in C# that can print to console first found solution.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication1
{
class Program
{
static List<string> resultString = new List<string>();
static bool CanDo(int n, int [] arr)
{
if (arr.Length == 1)
{
if (n % arr[0] == 0)
{
resultString.Add(n/ arr[0] + "*" + arr[0]);
return true;
}
}
else
{
var ls = new List<int>(arr);
ls.RemoveAt(0);
int [] newarr = ls.ToArray(); //Create New array by deleting first element of old array
for(int i = 0; i <= n/arr[0]; i++)
{
if (resultString.Count > 0)
{
resultString.RemoveAt(resultString.Count - 1);
}
int next_n = n - i * arr[0];
if (next_n == 0)
{
resultString.Add(i + "*" + arr[0]);
return true;
}
else if (next_n < 0)
{
break;
}
else if(next_n > 0)
{
if (i != 0)
{
resultString.Add(i + "*" + arr[0] + " + ");
}
if( CanDo(next_n, newarr) )
{
return true;
}
}
}
}
return false;
}
static void Main(string[] args)
{
try
{
int[] arr = { 3, 5, 7 };
int N = 20;
resultString = new List<string>();
if (CanDo(N, arr))
{
resultString.ForEach(Console.WriteLine);
Console.Read();
}
else
{
Console.Write("Can't do");
Console.Read();
}
}
catch (Exception ex)
{
//handle exception
}
}
}
}