Old Top Coder riddle: Making a number by inserting +

Question

I am thinking about this topcoder problem.

Given a string of digits, find the minimum number of additions required for the string to equal some target n

Answer 1

I haven't given it much thought yet, but if you scroll down you can see a link to the contest it was from, and from there you can see the solvers' solutions. Here's one in C#.

using System; 
using System.Text; 
using System.Text.RegularExpressions; 
using System.Collections; 

public class QuickSums { 
    public int minSums(string numbers, int sum) { 
        int[] arr = new int[numbers.Length]; 
    for (int i = 0 ; i < arr.Length; i++)       
      arr[i] = 0; 

    int min = 15; 

    while (arr[arr.Length - 1] != 2)     
    { 
      arr[0]++; 
      for (int i = 0; i < arr.Length - 1; i++) 
        if (arr[i] == 2)  
        { 
          arr[i] = 0; 
          arr[i + 1]++; 
        } 

      String newString = ""; 
      for (int i = 0; i < numbers.Length; i++) 
      { 
        newString+=numbers[i]; 
        if (arr[i] == 1) 
          newString+="+"; 
      } 

      String[] nums = newString.Split('+'); 
      int sum1 = 0; 
      for (int i = 0; i < nums.Length; i++) 
        try  
        { 
          sum1 += Int32.Parse(nums[i]); 
        } 
        catch 
        { 
        } 

      if (sum == sum1 && nums.Length - 1 < min) 
        min = nums.Length - 1; 
    } 

    if (min == 15) 
      return -1; 

    return min; 
  } 

}