445. 两数相加 II

445. 两数相加 II

题解

辅助栈

class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        Stack<ListNode> stack1 = new Stack<>();
        Stack<ListNode> stack2 = new Stack<>();
        while (l1 != null) {
            stack1.push(l1);
            l1 = l1.next;
        }
        while (l2 != null) {
            stack2.push(l2);
            l2 = l2.next;
        }
        // 记录是否进位
        int tip = 0;
        ListNode ans = null;
        while (!stack1.isEmpty() || !stack2.isEmpty() || tip != 0) {
            int l1Val = stack1.isEmpty() ? 0 : stack1.pop().val;
            int l2Val = stack2.isEmpty() ? 0 : stack2.pop().val;
            int sum = l1Val + l2Val + tip;
            tip = sum / 10;
            ListNode curNode = new ListNode(sum % 10);
            curNode.next = ans;
            ans = curNode;
        }
        return ans;
    }
}