I was giving this hiring contest ( already over ). I am stuck at this question. Needed some help

I am struggling to find a good article on implementing trie using array. I did get some code implementing the same and attempted to read them but unable to beat my doubts!!! Please share the idea or link of some good article.

In Codeforces Round #538 (Div. 2), I submitted the solution for problem C and got WA on test case 4 ( solution link ). I checked it offline and it gave correct output for test case 4. I also checked it on online compiler ideone, and it also gave the correct result. I tried submitting in different versions of C++ ( an illogical attempt and so )... failed. Please help me to find the cause of ambiguity ?