Convert Binary Number in a Linked List to Integer LeetCode solution in C++

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class Solution {
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 public:
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  int getDecimalValue(ListNode *head) {
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    ListNode *temp = head;
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    int count = 0;
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    while (temp->next != NULL) {
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      count++;
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      temp = temp->next;
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    }
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    temp = head;
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    int ans = 0;
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    while (count != -1) {
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      ans += temp->val * pow(2, count);
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      count--;
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      temp = temp->next;
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    }
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    return ans;
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  }
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};