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

* Add the intial translation of code of all the languages

* test

* revert

* Remove

* Add Python and Java code for EN version

en/codes/java/chapter_dynamic_programming/knapsack.java

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+/**
+ * File: knapsack.java
+ * Created Time: 2023-07-10
+ * Author: krahets (krahets@163.com)
+ */
+
+package chapter_dynamic_programming;
+
+import java.util.Arrays;
+
+public class knapsack {
+
+    /* 0-1 Knapsack: Brute force search */
+    static int knapsackDFS(int[] wgt, int[] val, int i, int c) {
+        // If all items have been chosen or the knapsack has no remaining capacity, return value 0
+        if (i == 0 || c == 0) {
+            return 0;
+        }
+        // If exceeding the knapsack capacity, can only choose not to put it in the knapsack
+        if (wgt[i - 1] > c) {
+            return knapsackDFS(wgt, val, i - 1, c);
+        }
+        // Calculate the maximum value of not putting in and putting in item i
+        int no = knapsackDFS(wgt, val, i - 1, c);
+        int yes = knapsackDFS(wgt, val, i - 1, c - wgt[i - 1]) + val[i - 1];
+        // Return the greater value of the two options
+        return Math.max(no, yes);
+    }
+
+    /* 0-1 Knapsack: Memoized search */
+    static int knapsackDFSMem(int[] wgt, int[] val, int[][] mem, int i, int c) {
+        // If all items have been chosen or the knapsack has no remaining capacity, return value 0
+        if (i == 0 || c == 0) {
+            return 0;
+        }
+        // If there is a record, return it
+        if (mem[i][c] != -1) {
+            return mem[i][c];
+        }
+        // If exceeding the knapsack capacity, can only choose not to put it in the knapsack
+        if (wgt[i - 1] > c) {
+            return knapsackDFSMem(wgt, val, mem, i - 1, c);
+        }
+        // Calculate the maximum value of not putting in and putting in item i
+        int no = knapsackDFSMem(wgt, val, mem, i - 1, c);
+        int yes = knapsackDFSMem(wgt, val, mem, i - 1, c - wgt[i - 1]) + val[i - 1];
+        // Record and return the greater value of the two options
+        mem[i][c] = Math.max(no, yes);
+        return mem[i][c];
+    }
+
+    /* 0-1 Knapsack: Dynamic programming */
+    static int knapsackDP(int[] wgt, int[] val, int cap) {
+        int n = wgt.length;
+        // Initialize dp table
+        int[][] dp = new int[n + 1][cap + 1];
+        // 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] = Math.max(dp[i - 1][c], dp[i - 1][c - wgt[i - 1]] + val[i - 1]);
+                }
+            }
+        }
+        return dp[n][cap];
+    }
+
+    /* 0-1 Knapsack: Space-optimized dynamic programming */
+    static int knapsackDPComp(int[] wgt, int[] val, int cap) {
+        int n = wgt.length;
+        // Initialize dp table
+        int[] dp = new int[cap + 1];
+        // State transition
+        for (int i = 1; i <= n; i++) {
+            // Traverse in reverse order
+            for (int c = cap; c >= 1; c--) {
+                if (wgt[i - 1] <= c) {
+                    // The greater value between not choosing and choosing item i
+                    dp[c] = Math.max(dp[c], dp[c - wgt[i - 1]] + val[i - 1]);
+                }
+            }
+        }
+        return dp[cap];
+    }
+
+    public static void main(String[] args) {
+        int[] wgt = { 10, 20, 30, 40, 50 };
+        int[] val = { 50, 120, 150, 210, 240 };
+        int cap = 50;
+        int n = wgt.length;
+
+        // Brute force search
+        int res = knapsackDFS(wgt, val, n, cap);
+        System.out.println("The maximum value within the bag capacity is " + res);
+
+        // Memoized search
+        int[][] mem = new int[n + 1][cap + 1];
+        for (int[] row : mem) {
+            Arrays.fill(row, -1);
+        }
+        res = knapsackDFSMem(wgt, val, mem, n, cap);
+        System.out.println("The maximum value within the bag capacity is " + res);
+
+        // Dynamic programming
+        res = knapsackDP(wgt, val, cap);
+        System.out.println("The maximum value within the bag capacity is " + res);
+
+        // Space-optimized dynamic programming
+        res = knapsackDPComp(wgt, val, cap);
+        System.out.println("The maximum value within the bag capacity is " + res);
+    }
+}