Creating a Directed Graph and longest path in C programming

Suppose the n rectangles are labeled 1 through n, a sequence is a permutation of the n integers. Consider a problem instance of 8 rectangles, (1,7,4,5,2,6,3,8) is a sequence, and (8,4,7,2,5,3,6,1) is also a sequence. Together, they form a sequence pair SP((1,7,4,5,2,6,3,8),(8,4,7,2,5,3,6,1)). The order in which a rectangle appear in the two sequences determines its relative positions with respect to other rectangles. Given a rectangle x in a sequence pair SP(S1, S2), the list of rectangles that appear before x in both S1 and S2 are located to the left of x in the packing. All rectangles that appear after x in both S1 and S2 are located to the right of x in the packing. Rectangles that appear after x in S1 but before x in S2 are located below x in the packing. Rectangles that appear before x in S1 but after x in S2 are located above x in the packing