translation: Add Python and Java code for EN version (#1345)

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* Add Python and Java code for EN version

en/codes/python/chapter_graph/graph_adjacency_matrix.py

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+"""
+File: graph_adjacency_matrix.py
+Created Time: 2023-02-23
+Author: krahets (krahets@163.com)
+"""
+
+import sys
+from pathlib import Path
+
+sys.path.append(str(Path(__file__).parent.parent))
+from modules import Vertex, print_matrix
+
+
+class GraphAdjMat:
+    """Undirected graph class based on adjacency matrix"""
+
+    def __init__(self, vertices: list[int], edges: list[list[int]]):
+        """Constructor"""
+        # Vertex list, elements represent "vertex value", index represents "vertex index"
+        self.vertices: list[int] = []
+        # Adjacency matrix, row and column indices correspond to "vertex index"
+        self.adj_mat: list[list[int]] = []
+        # Add vertex
+        for val in vertices:
+            self.add_vertex(val)
+        # Add edge
+        # Please note, edges elements represent vertex indices, corresponding to vertices elements indices
+        for e in edges:
+            self.add_edge(e[0], e[1])
+
+    def size(self) -> int:
+        """Get the number of vertices"""
+        return len(self.vertices)
+
+    def add_vertex(self, val: int):
+        """Add vertex"""
+        n = self.size()
+        # Add new vertex value to the vertex list
+        self.vertices.append(val)
+        # Add a row to the adjacency matrix
+        new_row = [0] * n
+        self.adj_mat.append(new_row)
+        # Add a column to the adjacency matrix
+        for row in self.adj_mat:
+            row.append(0)
+
+    def remove_vertex(self, index: int):
+        """Remove vertex"""
+        if index >= self.size():
+            raise IndexError()
+        # Remove vertex at `index` from the vertex list
+        self.vertices.pop(index)
+        # Remove the row at `index` from the adjacency matrix
+        self.adj_mat.pop(index)
+        # Remove the column at `index` from the adjacency matrix
+        for row in self.adj_mat:
+            row.pop(index)
+
+    def add_edge(self, i: int, j: int):
+        """Add edge"""
+        # Parameters i, j correspond to vertices element indices
+        # Handle index out of bounds and equality
+        if i < 0 or j < 0 or i >= self.size() or j >= self.size() or i == j:
+            raise IndexError()
+        # In an undirected graph, the adjacency matrix is symmetric about the main diagonal, i.e., satisfies (i, j) == (j, i)
+        self.adj_mat[i][j] = 1
+        self.adj_mat[j][i] = 1
+
+    def remove_edge(self, i: int, j: int):
+        """Remove edge"""
+        # Parameters i, j correspond to vertices element indices
+        # Handle index out of bounds and equality
+        if i < 0 or j < 0 or i >= self.size() or j >= self.size() or i == j:
+            raise IndexError()
+        self.adj_mat[i][j] = 0
+        self.adj_mat[j][i] = 0
+
+    def print(self):
+        """Print adjacency matrix"""
+        print("Vertex list =", self.vertices)
+        print("Adjacency matrix =")
+        print_matrix(self.adj_mat)
+
+
+"""Driver Code"""
+if __name__ == "__main__":
+    # Initialize undirected graph
+    # Please note, edges elements represent vertex indices, corresponding to vertices elements indices
+    vertices = [1, 3, 2, 5, 4]
+    edges = [[0, 1], [0, 3], [1, 2], [2, 3], [2, 4], [3, 4]]
+    graph = GraphAdjMat(vertices, edges)
+    print("\nAfter initialization, the graph is")
+    graph.print()
+
+    # Add edge
+    # Indices of vertices 1, 2 are 0, 2 respectively
+    graph.add_edge(0, 2)
+    print("\nAfter adding edge 1-2, the graph is")
+    graph.print()
+
+    # Remove edge
+    # Indices of vertices 1, 3 are 0, 1 respectively
+    graph.remove_edge(0, 1)
+    print("\nAfter removing edge 1-3, the graph is")
+    graph.print()
+
+    # Add vertex
+    graph.add_vertex(6)
+    print("\nAfter adding vertex 6, the graph is")
+    graph.print()
+
+    # Remove vertex
+    # Index of vertex 3 is 1
+    graph.remove_vertex(1)
+    print("\nAfter removing vertex 3, the graph is")
+    graph.print()