How do we solve this problem in Java language? Thank you!  We can describe the physical structure of some designs using an undirected graph. We’ll say vertex i is part of a triangle if i has two different neighbors j and k such that j and k are neighbors of each other. For this problem, find weak vertices in graphs – those vertices that is not part of any triangle. Figure 1: An illustration of the weak vertices (which are shaded) from the sample input graph.   Input Input consists of up to 100 graphs. Each starts with an integer, 1 ≤ n ≤ 20, giving the number of vertices in the graph. Next come n lines with n integers on each line, which describe an n×n adjacency matrix for the graph. Vertices are numbered from 0 to n−1. If the adjacency matrix contains a one at row r, column c (where 0 ≤ r, c ≤ n−1), it means that there is an edge from vertex r to vertex c. Since the graph is undirected, the adjacency matrix is symmetric. The end of input is marked by a value of −1 for n. Output For each graph, produce a line listing the weak vertices ordered from least to greatest.