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// 2816. Double a Number Represented as a Linked List
#include "leetcode.h"
/*
* given the 'head' of a non-empty linked list representing a non negative
* integer without leading zeros. return the 'head' of the linked list after
* doubling it.
*/
struct ListNode {
int val;
struct ListNode *next;
};
int depth(struct ListNode *head) {
int n = 0;
struct ListNode *tmp = head;
while (tmp) {
tmp = tmp->next;
n++;
}
return n;
}
struct ListNode *gen_list(int *arr, int len) {
struct ListNode *head = (struct ListNode *)malloc(sizeof(struct ListNode));
struct ListNode *node = head;
for (int i = 0; i < len; i++)
if ((!i && arr[i]) || i) {
node->val = arr[i];
if (i == len - 1)
break;
struct ListNode *tmp = (struct ListNode *)malloc(sizeof(struct ListNode));
node->next = tmp;
node = node->next;
}
node->next = NULL;
return head;
}
struct ListNode *doubleIt(struct ListNode *head) {
int n = depth(head) + 1, *arr = (int *)calloc(n, sizeof(int));
struct ListNode *tmp = head;
for (int i = 1; i < n; i++) {
arr[i] = tmp->val << 1;
tmp = tmp->next;
}
int j = 0;
for (int i = n - 1; i >= 0; i--) {
if (arr[i] >= 10) {
arr[i] += j;
j = arr[i] / 10;
arr[i] %= 10;
} else {
arr[i] += j;
j = 0;
}
}
struct ListNode *ans = gen_list(arr, n);
free(arr);
return ans;
}
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