哈希表

59 有效变位词

力扣https://leetcode-cn.com/problems/dKk3P7/

func isAnagram(s string, t string) bool {
	if len(s) != len(t) || s == t {
        //需要字符数相同但是字符顺序不相同
		return false
	}
	varmap := make(map[uint8]int)
	for i := 0; i < len(s); i++ {
		varmap[s[i]]++
		varmap[t[i]]--
	}
	for _, v := range varmap {
		if v != 0 {
			return false
		}
	}
	return true
}

60 变位词组

力扣https://leetcode-cn.com/problems/sfvd7V/

//抽象字符串的表示
func getNumberOfStr(str string)string{
	var arr [26]int
	for i:=0;i<len(str);i++{
		arr[str[i]-'a']++
	}
	var snum string
	for i:=0;i<len(arr);i++{
		tmp:= strconv.Itoa(arr[i])
		snum = snum + tmp + "#"
	}
	return snum
}

func groupAnagrams(strs []string) [][]string {
	var res [][]string
	strmap:=make(map[string][]string)
	for i:=0;i<len(strs);i++{
		strmap[getNumberOfStr(strs[i])] = append(strmap[getNumberOfStr(strs[i])] ,strs[i])
	}
	for _,v:=range strmap{
		res = append(res,v)
	}
	return res
}

61 外星语言是否排序

力扣https://leetcode-cn.com/problems/lwyVBB/

//a是否小于b
func compareByOrder(a,b string,score map[uint8]int)bool{
	lengtha:=len(a)
	lengthb:=len(b)
	if lengtha<lengthb{
		for i:=0;i<lengtha;i++{
			ascore:=score[a[i]]
			bscore:=score[b[i]]
			if ascore>bscore{
				return false
			}else if ascore==bscore{
				continue
			}else{
				return true
			}
		}
		return true
	}else {
		for i:=0;i<lengthb;i++{
			ascore:=score[a[i]]
			bscore:=score[b[i]]
			if ascore>bscore{
				return false
			}else if ascore==bscore{
				continue
			}else{
				return true
			}
		}
		if lengtha==lengthb{
			return true
		}
		return false
	}
}

func isAlienSorted(words []string, order string) bool {
	score:=make(map[uint8]int)
	for i:=0;i<len(order);i++{
		score[order[i]] = i
	}
// 抽象字符顺序的分数
	for i:=0;i<len(words)-1;i++{
		if !compareByOrder(words[i],words[i+1],score){
			return false
		}
	}
	return true
}

62 最小时间差

力扣https://leetcode-cn.com/problems/569nqc/

//核心是时间的计算
func findMinDifference(timePoints []string) int {
	if len(timePoints) > 24*60 {
		return 0
	}
	var mins []int
	for _, t := range timePoints {
		time := strings.Split(t, ":")
		h, _ := strconv.Atoi(time[0])
		m, _ := strconv.Atoi(time[1])
		mins = append(mins, h*60+m)
	}
	sort.Ints(mins)
	mins = append(mins, mins[0]+24*60)
	res := 24 * 60
	for i := 1; i < len(mins); i++ {
		res = min(res, mins[i]-mins[i-1])
	}
	return res
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

栈

63 后缀表达式后缀表达式https://leetcode-cn.com/problems/8Zf90G/

func calnum(a,b,fu string)int{
	a1,_:=strconv.Atoi(a)
	b1,_:=strconv.Atoi(b)
	switch fu {
	case "+":
		return a1+b1
	case "-":
		return a1-b1
	case "*":
		return a1*b1
	case "/":
		return a1/b1
	default:
		return 0
	}
}

func evalRPN(tokens []string) int {
	fumap:=make(map[string]bool)
	fumap["+"] = true
	fumap["-"] = true
	fumap["*"] = true
	fumap["/"] = true
	var res int
	var arr []string
	for i:=0;i<len(tokens);i++{
		if fumap[tokens[i]]{
			res = calnum(arr[len(arr)-2],arr[len(arr)-1],tokens[i])
			arr = arr[0:len(arr)-2]
			arr = append(arr,strconv.Itoa(res))
		}else{
			arr = append(arr,tokens[i])
		}
	}
	if len(arr)>0{
		res,_ = strconv.Atoi(arr[0])
	}
	return res
}

 64 小行星碰撞

力扣https://leetcode-cn.com/problems/XagZNi/

func pushAsteroid(res []int,asteroid int)[]int{
	if len(res)==0{
		res = append(res,asteroid)
		return res
	}
	if res[len(res)-1]*asteroid > 0 ||res[len(res)-1]*asteroid < 0 && res[len(res)-1] < 0 {
		//同相，直接放入
		res = append(res,asteroid)
	}else{
		//逆向，肯定会撞
		index:=len(res) - 1
		for index>=0&&(res[index]*asteroid<0){
			tmp:=res[index] + asteroid
			if tmp*res[index]>0{
				//新加入的被撞碎了，原先的没有影响
				return res[0:index+1]
			}else if tmp*res[index]==0{
				//互相碎了
				return res[0:index]
			}else{
				//新加入的撞碎了原先的
				index--
				res = res[0:index+1]
			}
		}
		res = append(res,asteroid)
	}
	return res
}

func asteroidCollision(asteroids []int) []int{
	var res []int
	for i:=0;i<len(asteroids);i++{
		res = pushAsteroid(res,asteroids[i])
	}
	return res
}

 65 每日温度

力扣https://leetcode-cn.com/problems/iIQa4I/

func dailyTemperatures(temperatures []int) []int {
	res:=make([]int,len(temperatures))
	index:=[]int{}
	for i:=0;i<len(temperatures);i++{
		for len(index)>0&&temperatures[i]>temperatures[index[len(index)-1]]{
			res[index[len(index)-1]] = i-index[len(index)-1]
			index = index[:len(index)-1]
		}
		index = append(index,i)
	}
	return res
}