add solution for P21

generic-github-user · Nov 18, 2022 · ae0afb3 · ae0afb3
1 parent 11192da
commit ae0afb3
Showing 1 changed file with 32 additions and 0 deletions.
diff --git a/puzzles/project-euler/21.c b/puzzles/project-euler/21.c
@@ -0,0 +1,32 @@
+#include <stdio.h>
+
+int d(int x) {
+    int sum = 0;
+    printf("%6d : ", x);
+    // while (x > 1) {
+        for (int i=1; i<x; i++) {
+            if (x % i == 0) {
+                // x /= i;
+                sum += i;
+                printf(" %d", i);
+            }
+        }
+    // }
+    printf(" ~ %d\n", sum);
+    return sum;
+}
+
+int main() {
+    int n = 10000;
+    // int test[n];
+    int S = 0;
+    for (int i=1; i<n; i++) {
+        int di = d(i);
+        if (di < n && i != di && i == d(di)) {
+            printf("amicable pair: %d, %d\n", i, di);
+            S += i;
+        }
+    }
+    printf("%d\n", S);
+}
+