leetcode go語言版本，主要為了熟悉下語言

1. Two Sum

雙指標版本, O(NlogN)

func twoSum(nums []int, target int) []int {
    valResult := []int{}
    indexResult := []int{}
    i := 0
    j := len(nums) - 1
    temp := make([]int, len(nums))
    copy(temp, nums)
    sort.Ints(temp)
    for i < j {
        if temp[i] + temp[j] < target {
            i++
        } else if temp[i] + temp[j] > target {
            j--
        } else {
            valResult = append(valResult, temp[i], temp[j])
            break
        } 
    }
    for i := 0; i < len(nums); i++ {
        if nums[i] == valResult[0] || nums[i] == valResult[1] {
            indexResult = append(indexResult, i)
        }
    }
    return indexResult
}

hash查詢版本，理論O(N)

func twoSum(nums []int, target int) []int {
    hash := make(map[int]int)
    result := []int{}
    for i := 0; i < len(nums); i++ {
        if  j, ok := hash[target - nums[i]]; ok {
            result = append(result, j, i)
            return result   
        }
        hash[nums[i]] = i
    }
    return result
}

2. Add Two Numbers

要想辦法把程式碼寫簡潔...不要好幾個迴圈判斷...

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
    dummy := ListNode{}
    p := &dummy
    carry := 0
    for l1 != nil || l2 != nil || carry != 0 {
        p.Next = &ListNode{}
        p = p.Next
        tempVal := carry
        if l1 != nil {
            tempVal += l1.Val
            l1 = l1.Next
        }
        if l2 != nil {
            tempVal += l2.Val
            l2 = l2.Next
        }
        p.Val = tempVal % 10
        carry = tempVal / 10
    }
    return dummy.Next
}

3. Longest Substring Without Repeating Characters

hash裡面存byte可解決英文字元，存rune中文也可處理...

func lengthOfLongestSubstring(s string) int {
    hash := make(map[rune]int)
    left := 0
    result := 0
    for i, v := range []rune(s) {    
        if lastI, ok := hash[v]; ok && lastI >= left {
            left = lastI + 1
        }
        if result < (i - left + 1) {
            result = i - left + 1
        }
        hash[v] = i
    }
    return result
}