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

en/codes/cpp/chapter_dynamic_programming/unbounded_knapsack.cpp

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+/**
+ * File: unbounded_knapsack.cpp
+ * Created Time: 2023-07-11
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Complete knapsack: Dynamic programming */
+int unboundedKnapsackDP(vector<int> &wgt, vector<int> &val, int cap) {
+    int n = wgt.size();
+    // Initialize dp table
+    vector<vector<int>> dp(n + 1, vector<int>(cap + 1, 0));
+    // State transition
+    for (int i = 1; i <= n; i++) {
+        for (int c = 1; c <= cap; c++) {
+            if (wgt[i - 1] > c) {
+                // If exceeding the knapsack capacity, do not choose item i
+                dp[i][c] = dp[i - 1][c];
+            } else {
+                // The greater value between not choosing and choosing item i
+                dp[i][c] = max(dp[i - 1][c], dp[i][c - wgt[i - 1]] + val[i - 1]);
+            }
+        }
+    }
+    return dp[n][cap];
+}
+
+/* Complete knapsack: Space-optimized dynamic programming */
+int unboundedKnapsackDPComp(vector<int> &wgt, vector<int> &val, int cap) {
+    int n = wgt.size();
+    // Initialize dp table
+    vector<int> dp(cap + 1, 0);
+    // State transition
+    for (int i = 1; i <= n; i++) {
+        for (int c = 1; c <= cap; c++) {
+            if (wgt[i - 1] > c) {
+                // If exceeding the knapsack capacity, do not choose item i
+                dp[c] = dp[c];
+            } else {
+                // The greater value between not choosing and choosing item i
+                dp[c] = max(dp[c], dp[c - wgt[i - 1]] + val[i - 1]);
+            }
+        }
+    }
+    return dp[cap];
+}
+
+/* Driver code */
+int main() {
+    vector<int> wgt = {1, 2, 3};
+    vector<int> val = {5, 11, 15};
+    int cap = 4;
+
+    // Dynamic programming
+    int res = unboundedKnapsackDP(wgt, val, cap);
+    cout << "The maximum value within the bag capacity is " << res << endl;
+
+    // Space-optimized dynamic programming
+    res = unboundedKnapsackDPComp(wgt, val, cap);
+    cout << "The maximum value within the bag capacity is " << res << endl;
+
+    return 0;
+}