Consider the sequence of digits from 1 through N (N<=9) in increasing order:
1 2 3 4 … N
Insert either a ‘+’ (for addition) or a ‘-‘ (for subtraction) between each of the digits so that the resultant sum is zero. Print all possible combinations that sum to zero.
Example: Enter a number: 7
1+2-3+4-5-6+7=0
1+2-3-4+5+6-7=0
1-2+3+4-5+6-7=0
1-2-3-4-5+6+7=0