Triplet sum Array

[Ashish-Malik-2069288229772245 (Ashish Malik)]

Can we solve this question with O(n)?
https://hack.codingblocks.com/contests/c/509/215

[Abhishek-Vanjani-1385688111468238 (Abhishek Vanjani)]

Best solution i know is O(N^2). I dont think it can be solved in better complexity.