refactor 51

fishercoder1534 · fishercoder1534 · commit 8eb2c3a7e0a6 · 2020-05-02T06:22:38.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_51.java b/src/main/java/com/fishercoder/solutions/_51.java
@@ -3,91 +3,68 @@
 import java.util.ArrayList;
 import java.util.List;
 
-/**
- * 51. N-Queens
- *
- * The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.
-
- Given an integer n, return all distinct solutions to the n-queens puzzle.
- Each solution contains a distinct board configuration of the n-queens' placement, where 'Q' and '.' both indicate a queen and an empty space respectively.
-
- For example,
- There exist two distinct solutions to the 4-queens puzzle:
-
- [
- [".Q..",  // Solution 1
- "...Q",
- "Q...",
- "..Q."],
-
- ["..Q.",  // Solution 2
- "Q...",
- "...Q",
- ".Q.."]
- ]
- */
 public class _51 {
 
-  public static class Solution1 {
+    public static class Solution1 {
 
-    public List<List<String>> solveNQueens(int n) {
-      List<List<String>> result = new ArrayList<>();
-      if (n <= 0) {
-        return result;
-      }
-      search(n, new ArrayList<>(), result);
-      return result;
-    }
+        public List<List<String>> solveNQueens(int n) {
+            List<List<String>> result = new ArrayList<>();
+            if (n <= 0) {
+                return result;
+            }
+            search(n, new ArrayList<>(), result);
+            return result;
+        }
 
-    private void search(int n, ArrayList<Integer> col, List<List<String>> result) {
-      if (col.size() == n) {
-        result.add(drawChessBoard(col));
-        return;
-      }
+        private void search(int n, ArrayList<Integer> col, List<List<String>> result) {
+            if (col.size() == n) {
+                result.add(drawChessBoard(col));
+                return;
+            }
 
-      for (int i = 0; i < n; i++) {
-        if (!isValid(col, i)) {
-          continue;
+            for (int i = 0; i < n; i++) {
+                if (!isValid(col, i)) {
+                    continue;
+                }
+                col.add(i);
+                search(n, col, result);
+                col.remove(col.size() - 1);
+            }
         }
-        col.add(i);
-        search(n, col, result);
-        col.remove(col.size() - 1);
-      }
-    }
 
-    private boolean isValid(ArrayList<Integer> col, int next) {
-      int row = col.size();
-      for (int i = 0; i < row; i++) {
-        if (next == col.get(i)) {
-          return false;
-        }
+        private boolean isValid(ArrayList<Integer> col, int next) {
+            int row = col.size();
+            for (int i = 0; i < row; i++) {
+                if (next == col.get(i)) {
+                    return false;
+                }
 
-        if (i - row == col.get(i) - next) {
-          return false;
-        }
+                if (i - row == col.get(i) - next) {
+                    return false;
+                }
 
-        if (i - row == next - col.get(i)) {
-          return false;
+                if (i - row == next - col.get(i)) {
+                    return false;
+                }
+            }
+            return true;
         }
-      }
-      return true;
-    }
 
-    private ArrayList<String> drawChessBoard(ArrayList<Integer> col) {
-      ArrayList<String> chessBoard = new ArrayList<>();
+        private ArrayList<String> drawChessBoard(ArrayList<Integer> col) {
+            ArrayList<String> chessBoard = new ArrayList<>();
 
-      for (int i = 0; i < col.size(); i++) {
-        String row = "";
-        for (int j = 0; j < col.size(); j++) {
-          if (col.get(j) == i) {
-            row += "Q";
-          } else {
-            row += ".";
-          }
+            for (int i = 0; i < col.size(); i++) {
+                String row = "";
+                for (int j = 0; j < col.size(); j++) {
+                    if (col.get(j) == i) {
+                        row += "Q";
+                    } else {
+                        row += ".";
+                    }
+                }
+                chessBoard.add(row);
+            }
+            return chessBoard;
         }
-        chessBoard.add(row);
-      }
-      return chessBoard;
     }
-  }
 }
