当$$x\leqslant 0$$，原方程为：$$\left\textbar{} (-x+1)-(-x) \right\textbar-(-x+1)+(-x)=1$$，  即$$1+x-1-x=1$$，无解；  当$$0 ~\textless{} ~x\leqslant 1$$，原方程为：$$\left\textbar{} (1-x)-x \right\textbar-(1-x)+x=1$$，  即$$\left\textbar{} 1-2x \right\textbar-1+2x=1$$，这种情况下当$$0 ~\textless{} ~x\leqslant \frac{1}{2}$$ 时，$$1-2x-1+2x=1$$无解；  当$$\frac{1}{2} ~\textless{} ~x\leqslant 1$$，$$2x-1-1+2x=1$$，$$x=\frac{3}{4}$$；  当$$x ~\textless{} ~1$$，原方程为：$$\left\textbar{} (x-1)-x \right\textbar-(x-1)+x=1$$，  即$$1-(x-1)+x=1$$，无解．  故选$$\text{C}$$． 
满足$$\left\textbar{} \left\textbar{} x-1 \right\textbar-\left\textbar{} x \right\textbar-\left\textbar{} x-1 \right\textbar+\left\textbar{} x \right\textbar=1$$的$$x$$的值是．

1. $$0$$ 
2. $$\pm \frac{1}{4}$$ 
3. $$\frac{3}{4}$$ 
4. $$\pm \frac{3}{4}$$ 