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3.cpp

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+#include <stdio.h>
+#include <stdbool.h>
+
+bool panduan(int board[9][9]) {
+    for (int i = 0; i < 9; i++) {
+        bool row[10] = { 0 }, col[10] = { 0 }, block[10] = { 0 }; 
+        for (int j = 0; j < 9; j++) {
+            if (board[i][j] != 0) {
+                if (row[board[i][j]]) {
+                    printf("The number %d in row %d has been used!\n", board[i][j], i);
+                    return false;
+                }
+                row[board[i][j]] = true;
+            }
+           
+            if (board[j][i] != 0) {
+                if (col[board[j][i]]) {
+                    printf("The number %d in column %d has been used!\n", board[j][i], i);
+                    return false;
+                }
+                col[board[j][i]] = true;
+            }
+            
+            int blockRow = 3 * (i / 3), blockCol = 3 * (i % 3);
+            if (board[blockRow + j / 3][blockCol + j % 3] != 0) {
+                if (block[board[blockRow + j / 3][blockCol + j % 3]]) {
+                    printf("The number %d in block %d has been used!\n",
+                        board[blockRow + j / 3][blockCol + j % 3], (i / 3) * 3 + (i % 3));
+                    return false;
+                }
+                block[board[blockRow + j / 3][blockCol + j % 3]] = true;
+            }
+        }
+    }
+    return true;
+}