leetcode算法题--表示数值的字符串

原题链接：https://leetcode.cn/problems/biao-shi-shu-zhi-de-zi-fu-chuan-lcof/description/?envType=study-plan-v2&envId=coding-interviews

题目类型有点新颖，有限状态机

// CharType表示当前字符的类型
// State表示当前所处的状态
type State int
type CharType int

const (
    CHAR_SPACE CharType = iota
    CHAR_POINT
    CHAR_NUMBER
    CHAR_ECHAR 
    CHAR_SINGAL 
    CHAR_INVALID
)

func getType(ch byte) CharType {
    switch(ch){
        case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
            return CHAR_NUMBER
        case '.':
            return CHAR_POINT
        case '+', '-':
            return CHAR_SINGAL
//        case ' ':
//            return CHAR_SPACE
        case 'e', 'E':
            return CHAR_ECHAR
    } 

    return CHAR_INVALID
}

const (
    STATE_INIT State = iota
    STATE_INIT_POINT
    STATE_INIT_SINGAL
    STATE_NUMBER
    STATE_NUMBER_POINT
    STATE_POINT_NUMBER
    STATE_ECHAR
    STATE_ECHAR_NUMBER
    STATE_ECHAR_SINGAL
)


func isNumber(s string) bool {
    tranfer := map[State]map[CharType]State{
        STATE_INIT: {
            CHAR_SINGAL: STATE_INIT_SINGAL,
            CHAR_POINT: STATE_INIT_POINT,
            CHAR_NUMBER: STATE_NUMBER,
        }, 
        STATE_INIT_POINT: {
            CHAR_NUMBER: STATE_POINT_NUMBER,
        },
        STATE_NUMBER: {
            CHAR_NUMBER: STATE_NUMBER,
            CHAR_POINT: STATE_NUMBER_POINT,
            CHAR_ECHAR: STATE_ECHAR,
        },
        STATE_INIT_SINGAL: {
            CHAR_POINT: STATE_INIT_POINT, 
            CHAR_NUMBER: STATE_NUMBER, 
        },
        STATE_ECHAR: {
            CHAR_SINGAL: STATE_ECHAR_SINGAL,
            CHAR_NUMBER: STATE_ECHAR_NUMBER,
        },
        STATE_NUMBER_POINT: {
            CHAR_NUMBER: STATE_POINT_NUMBER,
            CHAR_ECHAR: STATE_ECHAR, 
        },
        STATE_POINT_NUMBER: {
            CHAR_NUMBER: STATE_POINT_NUMBER, 
            CHAR_ECHAR: STATE_ECHAR, 
        },
        STATE_ECHAR_NUMBER: {
            CHAR_NUMBER: STATE_ECHAR_NUMBER,
        }, 
        STATE_ECHAR_SINGAL: {
            CHAR_NUMBER: STATE_ECHAR_NUMBER,
        },
    }

    state := STATE_INIT
    ss := strings.TrimSpace(s)
    for i := range ss {
        ch := ss[i]
        ty := getType(ch)
        if ty == CHAR_INVALID {
            return false
        }
        if st, ok := tranfer[state][ty]; ok {
            state = st
        } else {
            return false
        }
    }

    switch state {
        case STATE_NUMBER, STATE_POINT_NUMBER, STATE_NUMBER_POINT, STATE_ECHAR_NUMBER:
            return true
    }

    return false
}