class Solution {
public:
bool isNumber(string s) {
}
};
65. 有效数字
有效数字（按顺序）可以分成以下几个部分：
'e' 或 'E' ，后面跟着一个 整数小数（按顺序）可以分成以下几个部分：
'+' 或 '-'）'.''.' ，后面再跟着至少一位数字'.' ，后面跟着至少一位数字整数（按顺序）可以分成以下几个部分：
'+' 或 '-'）部分有效数字列举如下：["2", "0089", "-0.1", "+3.14", "4.", "-.9", "2e10", "-90E3", "3e+7", "+6e-1", "53.5e93", "-123.456e789"]
部分无效数字列举如下：["abc", "1a", "1e", "e3", "99e2.5", "--6", "-+3", "95a54e53"]
给你一个字符串 s ，如果 s 是一个 有效数字 ，请返回 true 。
示例 1：
输入：s = "0" 输出：true
示例 2：
输入：s = "e" 输出：false
示例 3：
输入：s = "." 输出：false
提示：
1 <= s.length <= 20s 仅含英文字母（大写和小写），数字（0-9），加号 '+' ，减号 '-' ，或者点 '.' 。相似题目
原站题解
python3 解法, 执行用时: 52 ms, 内存消耗: 15.1 MB, 提交时间: 2021-06-17 10:16:09
class Solution:
def isNumber(self, s: str) -> bool:
return re.match("([+, -]?)(((\d+\.\d*)|(\.\d+))|\d+)([e, E][+, -]?\d+)?$", s) != None
golang 解法, 执行用时: 0 ms, 内存消耗: 5.3 MB, 提交时间: 2021-06-17 10:11:26
type State int
type CharType int
const (
STATE_INITIAL State = iota
STATE_INT_SIGN
STATE_INTEGER
STATE_POINT
STATE_POINT_WITHOUT_INT
STATE_FRACTION
STATE_EXP
STATE_EXP_SIGN
STATE_EXP_NUMBER
STATE_END
)
const (
CHAR_NUMBER CharType = iota
CHAR_EXP
CHAR_POINT
CHAR_SIGN
CHAR_ILLEGAL
)
func toCharType(ch byte) CharType {
switch ch {
case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
return CHAR_NUMBER
case 'e', 'E':
return CHAR_EXP
case '.':
return CHAR_POINT
case '+', '-':
return CHAR_SIGN
default:
return CHAR_ILLEGAL
}
}
func isNumber(s string) bool {
transfer := map[State]map[CharType]State{
STATE_INITIAL: map[CharType]State{
CHAR_NUMBER: STATE_INTEGER,
CHAR_POINT: STATE_POINT_WITHOUT_INT,
CHAR_SIGN: STATE_INT_SIGN,
},
STATE_INT_SIGN: map[CharType]State{
CHAR_NUMBER: STATE_INTEGER,
CHAR_POINT: STATE_POINT_WITHOUT_INT,
},
STATE_INTEGER: map[CharType]State{
CHAR_NUMBER: STATE_INTEGER,
CHAR_EXP: STATE_EXP,
CHAR_POINT: STATE_POINT,
},
STATE_POINT: map[CharType]State{
CHAR_NUMBER: STATE_FRACTION,
CHAR_EXP: STATE_EXP,
},
STATE_POINT_WITHOUT_INT: map[CharType]State{
CHAR_NUMBER: STATE_FRACTION,
},
STATE_FRACTION: map[CharType]State{
CHAR_NUMBER: STATE_FRACTION,
CHAR_EXP: STATE_EXP,
},
STATE_EXP: map[CharType]State{
CHAR_NUMBER: STATE_EXP_NUMBER,
CHAR_SIGN: STATE_EXP_SIGN,
},
STATE_EXP_SIGN: map[CharType]State{
CHAR_NUMBER: STATE_EXP_NUMBER,
},
STATE_EXP_NUMBER: map[CharType]State{
CHAR_NUMBER: STATE_EXP_NUMBER,
},
}
state := STATE_INITIAL
for i := 0; i < len(s); i++ {
typ := toCharType(s[i])
if _, ok := transfer[state][typ]; !ok {
return false
} else {
state = transfer[state][typ]
}
}
return state == STATE_INTEGER || state == STATE_POINT || state == STATE_FRACTION || state == STATE_EXP_NUMBER || state == STATE_END
}