Lesson 6

06/Optional03.c

@@ -0,0 +1,37 @@
+#include <stdio.h>
+
+int main() {
+    int root = 2;// 若一个数有奇数个因子，那么它一定是平方数
+    int possibleFactor = 0;
+    int factorCount = 0;
+    int factors[5] = {0};
+    int testee = 0;
+    factors[0] = 1;
+    printf("1~1000内只包含5个因子的数是:\n");
+    for (;root < 32; root++) {
+        //31^2 < 1000 ^ 32^2，只用考虑到31
+        testee = root*root;
+        factorCount = 0;
+
+        factors[2] = root;
+        factors[4] = testee;
+
+        for (possibleFactor = 2; (possibleFactor < root); possibleFactor++) {
+            if (testee % possibleFactor == 0) {
+                if (factorCount == 0) {
+                    factors[1] = possibleFactor;
+                    factors[3] = testee / possibleFactor;
+                    factorCount++;
+                }
+                else {
+                    factorCount++;
+                    break;
+                }
+            }
+        }
+        if (factorCount == 1) {
+            printf("%3d: %4d%4d%4d%4d%4d\n",testee, factors[0], factors[1], factors[2], factors[3], factors[4]);
+        }
+    }
+    return 0;
+}