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  • 65. Valid Number

    package LeetCode_65
    
    /**
     * 65. Valid Number
     * https://leetcode.com/problems/valid-number/description/
     *
     * Validate if a given string can be interpreted as a decimal number.
    Some examples:
    "0" => true
    " 0.1 " => true
    "abc" => false
    "1 a" => false
    "2e10" => true
    " -90e3   " => true
    " 1e" => false
    "e3" => false
    " 6e-1" => true
    " 99e2.5 " => false
    "53.5e93" => true
    " --6 " => false
    "-+3" => false
    "95a54e53" => false
    
    Note: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one.
    However, here is a list of characters that can be in a valid decimal number:
    Numbers 0-9
    Exponent - "e"
    Positive/negative sign - "+"/"-"
    Decimal point - "."
     * */
    class Solution {
        fun isNumber(s: String): Boolean {
            var eSeen = false
            var dotSeen = false
            var numSeen = false
            val s2 = s.trim()
            for (i in s2.indices) {
                val c = s2[i]
                if (c.isDigit()) {
                    numSeen = true
                } else if (c == 'e') {
                    if (!numSeen || eSeen) {
                        return false
                    }
                    eSeen = true
                    //for example "1e" is not valid, so while e has seen, need set numSeen to false
                    numSeen = false
                } else if (c == '.') {
                    if (dotSeen || eSeen) {
                        /*
                        * 1.dot cannot appear two times
                        * 2.just can appear after e, for example: 99e2.5 is not Valid
                        * */
                        return false
                    }
                    dotSeen = true
                } else if (c == '+' || c == '-') {
                    if (i != 0 && s2[i - 1] != 'e') {
                        /*
                        * + and -
                        * 1.can appear in first position
                        * 2.if appear after e, is valid, for example: "005047e+6" is valid
                        * */
                        return false
                    }
                } else {
                    //abc is not valid
                    return false
                }
            }
            return numSeen
        }
    }
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  • 原文地址:https://www.cnblogs.com/johnnyzhao/p/13176235.html
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