Renaming folders

chp3_process/collatz.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int collatz(int, int[], int);
+void print_buffer(int buff[]);
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    perror("Usage: collatz NUMBER\n");
+    return EXIT_FAILURE;
+  }
+
+  int n = atoi(argv[1]);
+  if (n <= 1) {
+    perror("The number MUST be greater than 1\n");
+    return EXIT_FAILURE;
+  }
+
+  printf("Collatz of %d\n", n);
+
+  pid_t pid = fork();
+  if (pid == 0) {
+    int buff[1024] = {0};
+    collatz(n, buff, 0);
+    print_buffer(buff);
+  } else if (pid > 0) {
+    wait(NULL);
+  }
+
+  return EXIT_SUCCESS;
+}
+
+int collatz(int n, int buff[], int steps) {
+  buff[steps] = n;
+  if (n == 1) {
+    return n;
+  } else if (n % 2 == 0) {
+    return collatz(n / 2, buff, steps + 1);
+  } else {
+    return collatz(3 * n + 1, buff, steps + 1);
+  }
+}
+
+void print_buffer(int buff[]) {
+  int i = 0;
+  while (buff[i] != 0) {
+    printf("%d ", buff[i]);
+    i++;
+  }
+  printf("\n");
+}