第七课选做题。

07/Optional03.c

@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <stdbool.h>
+
+bool digits[10] = { 0 };
+
+bool checkDigit(int origin, int toBeChecked) {
+    bool originDigit[10] = { 0 }, toBeCheckedDigit[10] = { 0 };
+    int i = 0;
+    while (toBeChecked > 0) {
+        if (toBeCheckedDigit[toBeChecked % 10] == true) {
+            return false;
+        }
+        else {
+            toBeCheckedDigit[toBeChecked % 10] = true;
+        }
+        toBeChecked /= 10;
+    }
+    while (origin > 0) {
+        originDigit[origin % 10] = true;
+        origin /= 10;
+    }
+    while (i < 10) {
+        if (originDigit[i] != toBeCheckedDigit[i]) {
+            return false;
+        }
+        i++;
+    }
+    return true;
+}
+
+void pickDigit(int layer, int picked) {
+    int i = 0;
+    if (layer == 7) {
+        // printf("%d\n", picked);
+        if (checkDigit(picked, 2 * picked) && checkDigit(picked, 3 * picked)) {
+            printf("%d\n", picked);
+        }
+    }
+    else if (layer == 1) {
+        for (i = 1; i <= 3; i++) {
+            digits[i] = true;
+            pickDigit(2, i);
+            digits[i] = false;
+        }
+    }
+    else {
+        for (i = 0; i <= 9; i++) {
+            if (digits[i] == false) {
+                digits[i] = true;
+                pickDigit(layer + 1, picked * 10 + i);
+                digits[i] = false;
+            }
+        }
+    }
+}
+
+int main() {
+    pickDigit(1, 0);
+    return 0;
+}