Add the initial EN translation for C++ code (#1346)

en/codes/cpp/chapter_graph/graph_adjacency_matrix.cpp

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+/**
+ * File: graph_adjacency_matrix.cpp
+ * Created Time: 2023-02-09
+ * Author: what-is-me (whatisme@outlook.jp)
+ */
+
+#include "../utils/common.hpp"
+
+/* Undirected graph class based on adjacency matrix */
+class GraphAdjMat {
+    vector<int> vertices;       // Vertex list, elements represent "vertex value", index represents "vertex index"
+    vector<vector<int>> adjMat; // Adjacency matrix, row and column indices correspond to "vertex index"
+
+  public:
+    /* Constructor */
+    GraphAdjMat(const vector<int> &vertices, const vector<vector<int>> &edges) {
+        // Add vertex
+        for (int val : vertices) {
+            addVertex(val);
+        }
+        // Add edge
+        // Edges elements represent vertex indices
+        for (const vector<int> &edge : edges) {
+            addEdge(edge[0], edge[1]);
+        }
+    }
+
+    /* Get the number of vertices */
+    int size() const {
+        return vertices.size();
+    }
+
+    /* Add vertex */
+    void addVertex(int val) {
+        int n = size();
+        // Add new vertex value to the vertex list
+        vertices.push_back(val);
+        // Add a row to the adjacency matrix
+        adjMat.emplace_back(vector<int>(n, 0));
+        // Add a column to the adjacency matrix
+        for (vector<int> &row : adjMat) {
+            row.push_back(0);
+        }
+    }
+
+    /* Remove vertex */
+    void removeVertex(int index) {
+        if (index >= size()) {
+            throw out_of_range("Vertex does not exist");
+        }
+        // Remove vertex at `index` from the vertex list
+        vertices.erase(vertices.begin() + index);
+        // Remove the row at `index` from the adjacency matrix
+        adjMat.erase(adjMat.begin() + index);
+        // Remove the column at `index` from the adjacency matrix
+        for (vector<int> &row : adjMat) {
+            row.erase(row.begin() + index);
+        }
+    }
+
+    /* Add edge */
+    // Parameters i, j correspond to vertices element indices
+    void addEdge(int i, int j) {
+        // Handle index out of bounds and equality
+        if (i < 0 || j < 0 || i >= size() || j >= size() || i == j) {
+            throw out_of_range("Vertex does not exist");
+        }
+        // In an undirected graph, the adjacency matrix is symmetric about the main diagonal, i.e., satisfies (i, j) == (j, i)
+        adjMat[i][j] = 1;
+        adjMat[j][i] = 1;
+    }
+
+    /* Remove edge */
+    // Parameters i, j correspond to vertices element indices
+    void removeEdge(int i, int j) {
+        // Handle index out of bounds and equality
+        if (i < 0 || j < 0 || i >= size() || j >= size() || i == j) {
+            throw out_of_range("Vertex does not exist");
+        }
+        adjMat[i][j] = 0;
+        adjMat[j][i] = 0;
+    }
+
+    /* Print adjacency matrix */
+    void print() {
+        cout << "Vertex list = ";
+        printVector(vertices);
+        cout << "Adjacency matrix =" << endl;
+        printVectorMatrix(adjMat);
+    }
+};
+
+/* Driver Code */
+int main() {
+    /* Initialize undirected graph */
+    // Edges elements represent vertex indices
+    vector<int> vertices = {1, 3, 2, 5, 4};
+    vector<vector<int>> edges = {{0, 1}, {0, 3}, {1, 2}, {2, 3}, {2, 4}, {3, 4}};
+    GraphAdjMat graph(vertices, edges);
+    cout << "\nAfter initialization, the graph is" << endl;
+    graph.print();
+
+    /* Add edge */
+    // Indices of vertices 1, 2 are 0, 2 respectively
+    graph.addEdge(0, 2);
+    cout << "\nAfter adding edge 1-2, the graph is" << endl;
+    graph.print();
+
+    /* Remove edge */
+    // Indices of vertices 1, 3 are 0, 1 respectively
+    graph.removeEdge(0, 1);
+    cout << "\nAfter removing edge 1-3, the graph is" << endl;
+    graph.print();
+
+    /* Add vertex */
+    graph.addVertex(6);
+    cout << "\nAfter adding vertex 6, the graph is" << endl;
+    graph.print();
+
+    /* Remove vertex */
+    // Index of vertex 3 is 1
+    graph.removeVertex(1);
+    cout << "\nAfter removing vertex 3, the graph is" << endl;
+    graph.print();
+
+    return 0;
+}