The simplest solutions use integer weights, two hidden nodes with sign activation functions, purelin output activation functions and polar binary targets [-1 1 1 -1].
Since there are only 4 training equations for estimating (2+1)*2+(2+1)*1 = 9 weights, solutions are far from being unique without other constraints.
You can play around with the equations and determine your own version of "simplest solutions".
These can be easily transformed into solutions for continuous activation functions by replacing sign with tansig. The transformation of purelin to tansig or logsig is also straightforward.
Good Luck.
Greg
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