【英文】两数相加

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Preface

Add Two Numbers

Problem

Source Code

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package com;

import java.util.ArrayList;
import java.util.List;

public class ListNode {
    int val;
    ListNode next;
    ListNode() {}
    ListNode(int val) {
        this.val = val;
    }
    ListNode(int val, ListNode next) {
        this.val = val; this.next = next;
    }
}

class Solution {

    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

        // Convert the data of list1 to a string
        String s1 = "";
        ListNode point1 = l1;

        do {
            s1 += point1.val;
            point1 = point1.next;
        } while (point1!=null);

        // Convert the data of list2 to a string
        String s2 = "";
        ListNode point2 = l2;

        do {
            s2 += point2.val;
            point2 = point2.next;
        } while (point2!=null);

        // Find the string with the maximum length and the string with the minimum length
        String max = null;
        String min = null;
        if (s1.length() > s2.length()) {
            max = s1;
            min = s2;
        } else {
            max = s2;
            min = s1;
        }

        // Create an empty list to store the sum of the numbers
        List<Integer> list = new ArrayList<>();
        // Initialize the index of the maximum length string
        int i = 0;
        // Initialize the index of the minimum length string
        int j = 0;
        // Initialize the carry
        int pre = 0;
        // If the index of the long string has not exceeded the range, execute the outer loop
        while (i<max.length()) {
            int sum = 0;
            // If the index of the short string has not exceeded the range
            if (j<min.length()) {
                // Add the two numbers at the same position (i and j should be equal at this point) and the carry
                sum = Integer.parseInt(max.charAt(i)+"")+Integer.parseInt(min.charAt(j)+"")+pre;
            } else {
                // Add the number at the current position of the longer string and the carry
                sum = Integer.parseInt(max.charAt(i)+"")+pre;
            }
            // Reset the carry to zero
            pre = 0;
            String ssum = String.valueOf(sum);
            // Determine if the sum is a two-digit number
            if (ssum.length()==2) {
                // If it is a two-digit number, add the units digit to the list
                list.add(Integer.parseInt(ssum.charAt(1)+""));
                // At the same time, set the carry to 1
                pre = 1;
            } else if (ssum.length()==1) {
                // If it is a one-digit number, directly add the units digit to the list
                list.add(Integer.parseInt(ssum.charAt(0)+""));
            }
            // If there is still a carry in the last round, add the carry to the list
            if (i==max.length()-1 && pre==1) {
                list.add(1);
            }
            // Increase both indices by one in each loop
            i++;
            j++;
        }

        // Create an empty list node and store the result in it
        ListNode listNode = new ListNode();
        ListNode point = listNode;
        for (int k = 0; k < list.size(); k++) {
            point.val = list.get(k);
            if (k!=list.size()-1) {
                point.next = new ListNode();
                point = point.next;
            }
        }

        return listNode;

    }

}

Done