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i still dont get it..

i dont understand how can i keep track of the point of the last visited... and i tried queue.. i tried to place the digit that was not in sorted form in the queue. than i searched where the index is value is..and than replaced it if the sum is prime..
i also tried to solve it via permutation. i got ...

any one can explain me how i need to solve this problem.. i totally dont understand how i need to solve it.. i tried insertion sort on it.. but got WA. and how i can use BFS on it... any one care to explain me.. thanks in advance