[20250616] BOJ / G4 / 스도쿠 / 설진영

Seol-JY/202506/16 BOJ G4 스도쿠.md

@@ -0,0 +1,91 @@
+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+class Main {
+    private static int[] horizontalBit = new int[9];
+    private static int[] verticalBit = new int[9];
+    private static int[] sectionBit = new int[9];
+
+    private static int[][] map = new int[9][9];
+
+    private static int[] emptyRows = new int[81];
+    private static int[] emptyCols = new int[81];
+    private static int emptyCount = 0;
+
+    private static StringBuilder result = new StringBuilder();
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+
+        for (int i = 0; i < 9; i++) {
+            String line = br.readLine();
+            for (int j = 0; j < 9; j++) {
+                int num = line.charAt(j) - '0';
+                map[i][j] = num;
+
+                if (num == 0) {
+                    emptyRows[emptyCount] = i;
+                    emptyCols[emptyCount] = j;
+                    emptyCount++;
+                    continue;
+                }
+
+                int bitMask = 1 << (num - 1);
+                horizontalBit[i] |= bitMask;
+                verticalBit[j] |= bitMask;
+                sectionBit[getSectionNumber(i, j)] |= bitMask;
+            }
+        }
+
+        solve(0);
+
+        for (int i = 0; i < 9; i++) {
+            for (int j = 0; j < 9; j++) {
+                result.append(map[i][j]);
+            }
+            result.append('\n');
+        }
+        System.out.print(result);
+    }
+
+    private static boolean solve(int index) {
+        if (index == emptyCount) {
+            return true;
+        }
+
+        int row = emptyRows[index];
+        int col = emptyCols[index];
+        int sectionNum = getSectionNumber(row, col);
+
+        int usedBits = horizontalBit[row] | verticalBit[col] | sectionBit[sectionNum];
+
+        for (int num = 1; num <= 9; num++) {
+            int bitMask = 1 << (num - 1);
+
+            if ((usedBits & bitMask) == 0) {
+                map[row][col] = num;
+                horizontalBit[row] |= bitMask;
+                verticalBit[col] |= bitMask;
+                sectionBit[sectionNum] |= bitMask;
+
+                if (solve(index + 1)) {
+                    return true;
+                }
+
+                map[row][col] = 0;
+                horizontalBit[row] &= ~bitMask;
+                verticalBit[col] &= ~bitMask;
+                sectionBit[sectionNum] &= ~bitMask;
+            }
+        }
+
+        return false;
+    }
+
+    private static int getSectionNumber(int row, int col) {
+        return (row / 3) * 3 + (col / 3);
+    }
+}
+```