"Add Two Numbers": nothing, just want to be faster

Author: lennylxx

src/2.c

@@ -0,0 +1,102 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct ListNode {
+    int val;
+    struct ListNode *next;
+};
+
+struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {
+    if (l1 == NULL) return l2;
+    if (l2 == NULL) return l1;
+
+    struct ListNode *p1 = l1, *p2 = l2;
+    struct ListNode *ans = (struct ListNode *)calloc(1, sizeof(struct ListNode));
+    struct ListNode *p = ans, *last = NULL, *t = NULL;
+
+    int sum = 0;
+    while (1) {
+        if (p1 && p2) {
+            sum += p1->val + p2->val;
+            p1 = p1->next;
+            p2 = p2->next;
+        }
+        else if (p1 && (p2 == NULL)) {
+            sum += p1->val;
+            p1 = p1->next;
+        }
+        else if (p2 && (p1 == NULL)) {
+            sum += p2->val;
+            p2 = p2->next;
+        }
+        else {
+            break;
+        }
+
+        p->val = sum % 10;
+        sum /= 10;
+
+        /* for next node or the final node */
+        p->next = t = (struct ListNode *)calloc(1, sizeof(struct ListNode));
+        last = p;
+        p = p->next;
+    }
+
+    if (sum != 0) {
+        t->val = sum;
+    }
+    else {
+        /* sum is 0, we don't need a redundant 0, delete it */
+        free(t);
+        last->next = NULL;
+    }
+
+    return ans;
+}
+
+int main() {
+    struct ListNode *l1 = (struct ListNode *)calloc(3, sizeof(struct ListNode));
+    struct ListNode *p1 = l1;
+    p1->val = 2;
+    p1->next = p1 + 1;
+    p1++;
+
+    p1->val = 4;
+    p1->next = p1 + 1;
+    p1++;
+
+    p1->val = 5;
+    p1->next = NULL;
+
+    struct ListNode *l2 = (struct ListNode *)calloc(5, sizeof(struct ListNode));
+    struct ListNode *p2 = l2;
+    p2->val = 5;
+    p2->next = p2 + 1;
+    p2++;
+
+    p2->val = 6;
+    p2->next = p2 + 1;
+    p2++;
+
+    p2->val = 4;
+    p2->next = p2 + 1;
+    p2++;
+
+    p2->val = 9;
+    p2->next = p2 + 1;
+    p2++;
+
+    p2->val = 9;
+    p2->next = NULL;
+
+    struct ListNode *p = addTwoNumbers(l1, l2);
+    
+    /* 542 + 99465 = 100007 */
+    while (p != NULL) {
+        printf("%d ", p->val);
+        p = p->next;
+    }
+    printf("\n");
+
+    return 0;
+}