[20250717] BOJ / G4 / 스도쿠 / 이종환

Author: 0224LJH

0224LJH/202507/17 BOJ 스도쿠.md

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+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.Arrays;
+
+public class Main {
+    static int[][] arr;
+    static boolean finished = false;
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        arr = new int[9][9];
+        for (int i = 0; i < 9; i++) arr[i] = Arrays.stream(br.readLine().split("")).mapToInt(Integer::parseInt).toArray();
+        process();
+        print();
+    }
+
+
+
+    private static void print() {
+        for (int i = 0; i<9; i++) {
+            for (int j = 0; j < 9; j++) {
+                System.out.print(arr[i][j]);
+            }
+            System.out.println();
+        }
+    }
+
+    private static void process() {
+        int stY = -1;
+        int stX = -1;
+
+        outer:
+        for (int i = 0; i < 9; i++) {
+            for (int j = 0; j < 9; j++) {
+                if (arr[i][j] == 0) {
+                    stY = i;
+                    stX = j;
+                    break outer;
+                }
+            }
+        }
+        boolean[] nums = findAvailable(stY,stX);
+        for (int i = 1; i <= 9; i++) {
+            if (finished) return;
+            if (!nums[i])continue;
+            arr[stY][stX] = i;
+            sudoku(stY,stX);
+
+        }
+
+    }
+
+
+    private static void sudoku(int y, int x) {
+        int ny = -1;
+        int nx = -1;
+        outer:
+        for (int i = y; i < 9; i++) {
+            for (int j = 0; j < 9; j++) {
+                if(arr[i][j] != 0) continue;
+                else {
+                    ny = i;
+                    nx = j;
+                    break outer;
+                }
+            }
+        }
+        if(ny == -1 && nx == -1) {
+            finished = true;
+            return;
+        }
+
+        boolean[] nums = findAvailable(ny,nx);
+        for (int i = 1; i <= 9; i++) {
+            if (finished) return;
+            if (!nums[i])continue;
+            arr[ny][nx] = i;
+            sudoku(ny,nx);
+            if(!finished)arr[ny][nx] = 0;
+
+        }
+
+    }
+
+    private static boolean[] findAvailable(int stY, int stX) {
+        boolean[] ans = new boolean[10];
+        Arrays.fill(ans, true);
+        for (int i = 0; i < 9; i++) {
+            ans[arr[stY][i]] = false;
+            ans[arr[i][stX]] = false;
+        }
+
+        int pY = stY/3;
+        int pX = stX/3;
+        for (int i = pY*3; i < pY*3 + 3; i++) {
+            for (int j = pX*3; j < pX*3+3; j++) {
+                ans[arr[i][j]] = false;
+            }
+        }
+
+        return ans;
+    }
+
+
+}
+
+```