每日一题(2022-04-17)——最常见的单词

func mostCommonWord(paragraph string, banned []string) string {
	// 将banned存入map，便于后续判断当前单词是否被ban
	bannedMap :=make(map[string]int)
	for _, s := range banned {
		bannedMap[s] = 0
	}
	// 转小写
	paragraph = strings.ToLower(paragraph)
	// 段落单词切片,除去标点符号
	var wordSlice []string
	// 单个单词的字母切片
	var cSlice []rune
	for i, c := range paragraph {
		if c >= 'a' && c <= 'z' {
			cSlice = append(cSlice, c)
			// 遍历到了最后
			if i==len(paragraph)-1 {
				wordSlice = append(wordSlice, string(cSlice))
				break
			}
		} else { // 遇到非字母字符，将上面的rune切片转成字符串存入单词切片
			if string(cSlice) == " "||len(string(cSlice))==0 {
				cSlice = []rune{}
				continue
			} else {
				wordSlice = append(wordSlice, string(cSlice))
				cSlice = []rune{}
				continue
			}
		}
	}
	// 已经出现过的单词的次数
	already := make(map[string]int)
	max := 0
	result := ""
	for _, word := range wordSlice {
		// 如果被ban 直接下一个单词
		if _,ok:=bannedMap[word];ok==true {
			continue
		}
		// 如果不存在 加入map 次数初始化为1
		if _, ok := already[word]; ok == false {
			already[word] = 1
		}else {
			already[word]++
		}
		if already[word] > max {
			max = already[word]
			result = word
		}
	}
	return result
}