zoukankan      html  css  js  c++  java
  • Add Two Numbers

    You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

    Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
    Output: 7 -> 0 -> 8

    Analyse:

     1 /**
     2  * Definition for singly-linked list.
     3  * struct ListNode {
     4  *     int val;
     5  *     ListNode *next;
     6  *     ListNode(int x) : val(x), next(NULL) {}
     7  * };
     8  */
     9 class Solution {
    10 public:
    11     ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
    12         ListNode *head = new ListNode(0);
    13         ListNode *result = head;
    14         
    15         int carry = 0;
    16         int temp = 0;
    17         while(l1 || l2){
    18             if(!l1){
    19                 temp = l2->val + carry;
    20                 l2 = l2->next;
    21             }
    22             else if(!l2){
    23                 temp = l1->val + carry;
    24                 l1 = l1->next;
    25             }
    26             else{
    27                 int temp = l1->val + l2->val + carry;
    28                 l1 = l1->next;
    29                 l2 = l2->next;
    30             }
    31             carry = temp / 10;
    32             result->next = new ListNode(temp % 10);
    33             result = result->next;
    34         }
    35         if(carry){
    36             result->next = new ListNode(1);
    37             result = result->next;
    38         }
    39         return head->next;
    40     }
    41 };
    View Code

    The above code was wrong but I have not found the reason. OH MY GOD!! The only bug was the "int temp" in line 27!!!!!!! BE CAREFUL!!!! After correction, the run time is 60ms and is more efficient than the last code on this page. 

    /**
     * Definition for singly-linked list.
     * struct ListNode {
     *     int val;
     *     ListNode *next;
     *     ListNode(int x) : val(x), next(NULL) {}
     * };
     */
    class Solution {
    public:
        ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
            ListNode *head = new ListNode(0);
            ListNode *result = head;
            
            int carry = 0;
            int temp = 0;
            while(l1 || l2){
                if(!l1){
                    temp = l2->val + carry;
                    l2 = l2->next;
                }
                else if(!l2){
                    temp = l1->val + carry;
                    l1 = l1->next;
                }
                else{
                    temp = l1->val + l2->val + carry; //if there is an int before temp, it will go wrong
                    l1 = l1->next;
                    l2 = l2->next;
                }
                carry = temp / 10;
                result->next = new ListNode(temp % 10);
                result = result->next;
            }
            if(carry){
                result->next = new ListNode(1);
                result = result->next;
            }
            return head->next;
        }
    };

    The code below was 63ms on the judge platform of leetcode.

     1 /**
     2  * Definition for singly-linked list.
     3  * struct ListNode {
     4  *     int val;
     5  *     ListNode *next;
     6  *     ListNode(int x) : val(x), next(NULL) {}
     7  * };
     8  */
     9 class Solution {
    10 public:
    11     ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
    12         ListNode *head = new ListNode(0);
    13         ListNode *result = head;
    14         
    15         int carry = 0;
    16         while(l1 || l2){
    17             int val1 = 0;
    18             if(l1){
    19                 val1 = l1->val;
    20                 l1 = l1->next;
    21             }
    22             
    23             int val2 = 0;
    24             if(l2){
    25                 val2 = l2->val;
    26                 l2 = l2->next;
    27             }
    28             int temp = val1 + val2 + carry;
    29             result->next = new ListNode(temp % 10);
    30             carry = temp / 10;
    31             result = result->next;
    32         }
    33         if(carry)result->next = new ListNode(1);
    34         
    35         return head->next;
    36     }
    37 };
  • 相关阅读:
    java设计模式之建造者模式
    java设计模式之工厂模式
    Java并发—简介与线程创建
    Java基础—反射(转载)
    Eclipse中svn操作
    js常用方法总结
    Oracle学习笔记—常用函数
    Oracle学习笔记—connect、resource和dba三种权限(转载)
    JavaWeb—拦截器Interceptor
    JavaWeb—监听器Listener
  • 原文地址:https://www.cnblogs.com/amazingzoe/p/4439331.html
Copyright © 2011-2022 走看看