Update pset0

semester3/pset0/7-3-central-list.c

@@ -1,59 +1,52 @@
-#include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 
-typedef struct stack {
-  int val;
-  struct stack *next;
-} stack;
+typedef struct listNode {
+  int id;
+  struct listNode *next;
+} listNode;
 
-stack *push(stack *st, int val) {
-  stack *new = malloc(sizeof(stack));
-  new->next = st;
-  new->val = val;
+listNode *appendNode(int id, listNode *head) {
+  listNode *new = malloc(sizeof(listNode));
+  new->id = id;
+  new->next = NULL;
+
+  head->next = new;
   return new;
 }
 
-int isEmpty(stack *st) { return st == NULL; }
-
-int peek(stack *st) { return st->val; }
-
-stack *pop(stack *st) {
-  stack *tmp = st->next;
-  free(st);
-  return tmp;
-}
-
 int main(void) {
-  stack *st = NULL;
+  listNode* head = malloc(sizeof(listNode));
+  listNode* ptr = head;
 
   int size = 0;
-  int in;
-  int last;
-  int lastUsed = 0;
-  int centFound = 0;
-
-  while (scanf("%d,", &in) != EOF) {
+  int buf;
+  while ((scanf("%d,", & buf) != EOF)) {
+    ptr = appendNode(buf, ptr);
     size++;
-    if (!isEmpty(st) && peek(st) == in) {
-      st = pop(st);
-    } else if (lastUsed == 1 && last == in) {
-      st = pop(st);
-      st = pop(st);
-      centFound = 1;
-    } else {
-      if (!isEmpty(st)) {
-        last = peek(st);
-        lastUsed = 1;
-      }
-      // printf("PUSHING: %d\n", in);
-      st = push(st, in);
+  }
+
+  if (size <= 1) {
+    printf("Yes");
+    return 0;
+  }
+
+  int ans[size];
+
+  head = head->next;
+  for (int i = 0; i < size; i ++) {
+    ans[i] = head->id;
+    head = head->next;
+  }
+
+  int isCentral = 1;
+  for (int i = 0, end = size / 2; i < end; i++) {
+    if (ans[i] != ans[size - i - 1]) {
+      isCentral = 0;
     }
   }
 
-  if (size > 0 && isEmpty(st) && centFound == 1) {
-    printf("Yes");
-  } else if (size == 1) {
+  if (isCentral == 1) {
     printf("Yes");
   } else {
     printf("No");