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
2026-04-08 05:01:01 +08:00 · 2024-05-06 05:21:51 +08:00
parent b5e198db7d
commit 1c0f350ad6
174 changed files with 12349 additions and 0 deletions
--- a/en/codes/java/chapter_backtracking/n_queens.java
+++ b/en/codes/java/chapter_backtracking/n_queens.java
@@ -0,0 +1,77 @@
+/**
+ * File: n_queens.java
+ * Created Time: 2023-05-04
+ * Author: krahets (krahets@163.com)
+ */
+
+package chapter_backtracking;
+
+import java.util.*;
+
+public class n_queens {
+    /* Backtracking algorithm: n queens */
+    public static void backtrack(int row, int n, List<List<String>> state, List<List<List<String>>> res,
+            boolean[] cols, boolean[] diags1, boolean[] diags2) {
+        // When all rows are placed, record the solution
+        if (row == n) {
+            List<List<String>> copyState = new ArrayList<>();
+            for (List<String> sRow : state) {
+                copyState.add(new ArrayList<>(sRow));
+            }
+            res.add(copyState);
+            return;
+        }
+        // Traverse all columns
+        for (int col = 0; col < n; col++) {
+            // Calculate the main and minor diagonals corresponding to the cell
+            int diag1 = row - col + n - 1;
+            int diag2 = row + col;
+            // Pruning: do not allow queens on the column, main diagonal, or minor diagonal of the cell
+            if (!cols[col] && !diags1[diag1] && !diags2[diag2]) {
+                // Attempt: place the queen in the cell
+                state.get(row).set(col, "Q");
+                cols[col] = diags1[diag1] = diags2[diag2] = true;
+                // Place the next row
+                backtrack(row + 1, n, state, res, cols, diags1, diags2);
+                // Retract: restore the cell to an empty spot
+                state.get(row).set(col, "#");
+                cols[col] = diags1[diag1] = diags2[diag2] = false;
+            }
+        }
+    }
+
+    /* Solve n queens */
+    public static List<List<List<String>>> nQueens(int n) {
+        // Initialize an n*n size chessboard, where 'Q' represents the queen and '#' represents an empty spot
+        List<List<String>> state = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            List<String> row = new ArrayList<>();
+            for (int j = 0; j < n; j++) {
+                row.add("#");
+            }
+            state.add(row);
+        }
+        boolean[] cols = new boolean[n]; // Record columns with queens
+        boolean[] diags1 = new boolean[2 * n - 1]; // Record main diagonals with queens
+        boolean[] diags2 = new boolean[2 * n - 1]; // Record minor diagonals with queens
+        List<List<List<String>>> res = new ArrayList<>();
+
+        backtrack(0, n, state, res, cols, diags1, diags2);
+
+        return res;
+    }
+
+    public static void main(String[] args) {
+        int n = 4;
+        List<List<List<String>>> res = nQueens(n);
+
+        System.out.println("Input the dimensions of the chessboard as " + n);
+        System.out.println("Total number of queen placement solutions = " + res.size());
+        for (List<List<String>> state : res) {
+            System.out.println("--------------------");
+            for (List<String> row : state) {
+                System.out.println(row);
+            }
+        }
+    }
+}