Getting WA in Spoj problen:-BENEFACT — The Benefactor using DIjkstra but getting AC using BFS. Why?

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I am doing BENEFACT — The Benefactor.

I am using 2-time BFS method to calculate the longest path. Because here cost is associated with every edge so I am doing 2 times Dijkstra instead of 2 times BFS. But I am getting WA.

Can Anyone tell me Why I am getting WA?

Here is my code.

Edit:- Now I have done using BFS instead of Dijkstra and I got Ac. Here is my code.

I want to know why solution using Dijkstra give WA and BFS gives AC.

Can Anyone help me? Please