Generation of intermediate code based on an abstract machine model is useful in compilers because

Linked lists are not suitable data structures of which one of the following problems?

Which of the following permutations can be obtained in the output (in the same order) using a stack assuming that the input is the sequence 1, 2, 3, 4, 5 in that order?

In a compact single dimensional array representation for lower triangular matrices (i.e all the elements above the diagonal are zero) of size n $$\times$$ n, non-zero elements (i.e., elements of the lower triangle) of each row are stored one after another, starting from the first row, the index of the (i, j)^th element of the lower triangular matrix in this new representation is