Triangular Wave Current input to a capactior, Voltage Response?
You can assume that the rising edge of the triangle as I(t)=k*t and its integral V(t)=(1/2)t^2.
For the falling edge of the triangle, I(t)=1-Kt and its integral is t-(1/2)*t^2.
You need to add these responses (Applying Superposition and time shifting property of linear circuit principles). 
you get the response as shown in below picture.

Hope this helps.