Rotate list

Signed-off-by: Leo Ma <[email protected]>

061_rotate_list/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test rotate_list.c

061_rotate_list/rotate_list.c

@@ -0,0 +1,77 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct ListNode {
+    int val;
+    struct ListNode *next;
+};
+
+static struct ListNode* rotateRight(struct ListNode* head, int k) {
+    if (head == NULL || k <= 0) {
+        return head;
+    }
+
+    struct ListNode dummy;
+    dummy.next = head;
+    struct ListNode *prev = &dummy;
+    struct ListNode *last = &dummy;
+    struct ListNode *p = head;
+    int count = k;
+    while (k > 0) {
+        if (p == NULL) {
+            int length = count - k;
+            prev = &dummy;
+            p = head;
+            k = count % length;
+            if (k == 0) break;
+        }
+        prev = p;
+        p = p->next;
+        k--;
+    }
+
+    while (p != NULL) {
+        last = last->next;
+        prev = p;
+        p = p->next;
+    }
+
+    if (last != &dummy) {
+        prev->next = head;
+        dummy.next = last->next;
+        last->next = NULL;
+    }
+    return dummy.next;
+}
+
+int main(int argc, char **argv)
+{
+    int i;
+    struct ListNode *p, *prev, dummy, *list;
+
+    if (argc < 2) {
+        fprintf(stderr, "Usage: ./test k n1 n2...\n");
+        exit(-1);
+    }
+
+    dummy.next = NULL;
+    prev = &dummy;
+    for (i = 2; i < argc; i++) {
+        p = malloc(sizeof(*p));
+        int n = atoi(argv[i]);
+        printf("%d ", n);
+        p->val = n;
+        p->next = NULL;
+        prev->next = p;
+        prev = p;
+    }
+    putchar('\n');
+
+    list = rotateRight(dummy.next, atoi(argv[1]));
+    for (p = list; p != NULL; p = p->next) {
+        printf("%d ", p->val);
+    }
+    putchar('\n');
+
+    return 0;
+}