twoSum

给定一个整数数组 nums 和一个目标值 target，请你在该数组中找出和为目标值的那 两个 整数，并返回他们的数组下标。

你可以假设每种输入只会对应一个答案。但是，你不能重复利用这个数组中同样的元素。

示例:

给定 nums = [2, 7, 11, 15], target = 9

因为 nums[0] + nums[1] = 2 + 7 = 9
所以返回 [0, 1]

python

01_twosum.pyview raw
def two_sum(nums, target):
    d = {}
    for i, num in enumerate(nums):
        if target - num in d:
            return d[target - num], i
        d[num] = i

go

01_twosum.goview raw
func twoSum(nums []int, target int) []int {
	m := make(map[int]int)
	for i, num := range nums {
		complement := target - num
		if _, ok := m[complement]; ok {
			return []int{m[complement], i}
		}
		m[num] = i
	}
	return nil
}

addTwoNumbers

给你两个 非空 的链表，表示两个非负的整数。它们每位数字都是按照 逆序 的方式存储的，并且每个节点只能存储 一位 数字。

请你将两个数相加，并以相同形式返回一个表示和的链表。

你可以假设除了数字 0 之外，这两个数都不会以 0 开头。

示例 1：

输入：l1 = [2,4,3], l2 = [5,6,4]
输出：[7,0,8]
解释：342 + 465 = 807.

示例 2：

输入：l1 = [0], l2 = [0]
输出：[0]

示例 3：

输入：l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
输出：[8,9,9,9,0,0,0,1]

python

02-addTwoNumbers.pyview raw
from typing import Optional


class ListNode:
    def __init__(self, value: int, next: Optional["ListNode"] = None) -> None:
        self.value = value
        self.next = next

    def show(self) -> None:
        tmp = self
        _s = ""
        while tmp:
            _s += "%d -> " % tmp.value
            tmp = tmp.next

        _s = _s.rstrip(" -> ")
        print(_s)


def add_two_numbers(p1: ListNode, p2: ListNode) -> ListNode:
    carry = 0
    head: Optional[ListNode] = None
    current = head
    while p1 or p2 or carry:
        n1 = n2 = 0
        if p1:
            n1 = p1.value
            p1 = p1.next
        if p2:
            n2 = p2.value
            p2 = p2.next
        s = n1 + n2 + carry
        s, carry = s % 10, s // 10
        if head is None:
            head = ListNode(s)
            current = head
        else:
            current.next = ListNode(s)
            current = current.next
    return head

go

02-addTwoNumbers.goview raw
package base

import (
	"fmt"
	"strings"
)

type ListNode struct {
	Value int
	Next  *ListNode
}

func (h *ListNode) ShowNums() {
	s, tmp := "", h
	for tmp != nil {
		s += fmt.Sprintf("%d -> ", tmp.Value)
		tmp = tmp.Next
	}
	s = strings.TrimRight(s, " -> ")
	fmt.Println(s)
}

func AddTwoNumbers(p1 *ListNode, p2 *ListNode) (head *ListNode) {
	var tail *ListNode
	flag := 0
	for p1 != nil || p2 != nil || flag != 0 {
		n1, n2 := 0, 0

		if p1 != nil {
			n1 = p1.Value
			p1 = p1.Next
		}
		if p2 != nil {
			n2 = p2.Value
			p2 = p2.Next
		}
		sum := n1 + n2 + flag
		sum, flag = sum%10, sum/10

		if head == nil {
			head = &ListNode{Value: sum}
			tail = head
		} else {
			tail.Next = &ListNode{Value: sum}
			tail = tail.Next
		}

	}
	return
}