Data commit

Task/Weird-numbers/C/weird-numbers.c

@@ -0,0 +1,113 @@
+#include "stdio.h"
+#include "stdlib.h"
+#include "stdbool.h"
+#include "string.h"
+
+struct int_a {
+    int *ptr;
+    size_t size;
+};
+
+struct int_a divisors(int n) {
+    int *divs, *divs2, *out;
+    int i, j, c1 = 0, c2 = 0;
+    struct int_a array;
+
+    divs = malloc(n * sizeof(int) / 2);
+    divs2 = malloc(n * sizeof(int) / 2);
+    divs[c1++] = 1;
+
+    for (i = 2; i * i <= n; i++) {
+        if (n % i == 0) {
+            j = n / i;
+            divs[c1++] = i;
+            if (i != j) {
+                divs2[c2++] = j;
+            }
+        }
+    }
+
+    out = malloc((c1 + c2) * sizeof(int));
+    for (int i = 0; i < c2; i++) {
+        out[i] = divs2[i];
+    }
+    for (int i = 0; i < c1; i++) {
+        out[c2 + i] = divs[c1 - i - 1];
+    }
+    array.ptr = out;
+    array.size = c1 + c2;
+
+    free(divs);
+    free(divs2);
+    return array;
+}
+
+bool abundant(int n, struct int_a divs) {
+    int sum = 0;
+    int i;
+    for (i = 0; i < divs.size; i++) {
+        sum += divs.ptr[i];
+    }
+    return sum > n;
+}
+
+bool semiperfect(int n, struct int_a divs) {
+    if (divs.size > 0) {
+        int h = *divs.ptr;
+        int *t = divs.ptr + 1;
+
+        struct int_a ta;
+        ta.ptr = t;
+        ta.size = divs.size - 1;
+
+        if (n < h) {
+            return semiperfect(n, ta);
+        } else {
+            return n == h
+                || semiperfect(n - h, ta)
+                || semiperfect(n, ta);
+        }
+    } else {
+        return false;
+    }
+}
+
+bool *sieve(int limit) {
+    bool *w = calloc(limit, sizeof(bool));
+    struct int_a divs;
+    int i, j;
+
+    for (i = 2; i < limit; i += 2) {
+        if (w[i]) continue;
+        divs = divisors(i);
+        if (!abundant(i, divs)) {
+            w[i] = true;
+        } else if (semiperfect(i, divs)) {
+            for (j = i; j < limit; j += i) {
+                w[j] = true;
+            }
+        }
+    }
+
+    free(divs.ptr);
+    return w;
+}
+
+int main() {
+    bool *w = sieve(17000);
+    int count = 0;
+    int max = 25;
+    int n;
+
+    printf("The first 25 weird numbers:\n");
+    for (n = 2; count < max; n += 2) {
+        if (!w[n]) {
+            printf("%d ", n);
+            count++;
+        }
+    }
+    printf("\n");
+
+    free(w);
+    return 0;
+}