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

en/codes/cpp/chapter_computational_complexity/space_complexity.cpp

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+/**
+ * File: space_complexity.cpp
+ * Created Time: 2022-11-25
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Function */
+int func() {
+    // Perform some operations
+    return 0;
+}
+
+/* Constant complexity */
+void constant(int n) {
+    // Constants, variables, objects occupy O(1) space
+    const int a = 0;
+    int b = 0;
+    vector<int> nums(10000);
+    ListNode node(0);
+    // Variables in a loop occupy O(1) space
+    for (int i = 0; i < n; i++) {
+        int c = 0;
+    }
+    // Functions in a loop occupy O(1) space
+    for (int i = 0; i < n; i++) {
+        func();
+    }
+}
+
+/* Linear complexity */
+void linear(int n) {
+    // Array of length n occupies O(n) space
+    vector<int> nums(n);
+    // A list of length n occupies O(n) space
+    vector<ListNode> nodes;
+    for (int i = 0; i < n; i++) {
+        nodes.push_back(ListNode(i));
+    }
+    // A hash table of length n occupies O(n) space
+    unordered_map<int, string> map;
+    for (int i = 0; i < n; i++) {
+        map[i] = to_string(i);
+    }
+}
+
+/* Linear complexity (recursive implementation) */
+void linearRecur(int n) {
+    cout << "Recursion n = " << n << endl;
+    if (n == 1)
+        return;
+    linearRecur(n - 1);
+}
+
+/* Quadratic complexity */
+void quadratic(int n) {
+    // A two-dimensional list occupies O(n^2) space
+    vector<vector<int>> numMatrix;
+    for (int i = 0; i < n; i++) {
+        vector<int> tmp;
+        for (int j = 0; j < n; j++) {
+            tmp.push_back(0);
+        }
+        numMatrix.push_back(tmp);
+    }
+}
+
+/* Quadratic complexity (recursive implementation) */
+int quadraticRecur(int n) {
+    if (n <= 0)
+        return 0;
+    vector<int> nums(n);
+    cout << "Recursive n = " << n << ", length of nums = " << nums.size() << endl;
+    return quadraticRecur(n - 1);
+}
+
+/* Exponential complexity (building a full binary tree) */
+TreeNode *buildTree(int n) {
+    if (n == 0)
+        return nullptr;
+    TreeNode *root = new TreeNode(0);
+    root->left = buildTree(n - 1);
+    root->right = buildTree(n - 1);
+    return root;
+}
+
+/* Driver Code */
+int main() {
+    int n = 5;
+    // Constant complexity
+    constant(n);
+    // Linear complexity
+    linear(n);
+    linearRecur(n);
+    // Quadratic complexity
+    quadratic(n);
+    quadraticRecur(n);
+    // Exponential complexity
+    TreeNode *root = buildTree(n);
+    printTree(root);
+
+    // Free memory
+    freeMemoryTree(root);
+
+    return 0;
+}