剑指offer-题54：表示数值的字符串

柔光的暖阳◎ 2022-05-27 13:36 210阅读 0赞

## **题目描述** ##

请实现一个函数用来判断字符串是否表示数值（包括整数和小数）。例如，字符串”+100”,”5e2”,”-123”,”3.1416”和”-1E-16”都表示数值。但是”12e”,”1a3.14”,”1.2.3”,”+-5”和”12e+4.3”都不是。

实验平台：[牛客网][Link 1]

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## **解决思路：** ##

![这里写图片描述][70]

java:

public class Solution { 
        public boolean isNumeric(char[] str) {
            int strLenght = str.length;
            if (str == null || strLenght == 0) {
                return false;
            }
            int index = 0;
            if (str[index] == '+' || str[index] == '-') {
                index++;
            }
            if (index == strLenght) {
                return false;
            }
            // 整数0~9部分
            while (index < strLenght && str[index] >= '0' && str[index] <= '9') {
                index++;
            }
            if (index != strLenght) {
                if (str[index] == '.') {
       // 含有小数点时
                    index++;
                    while (index < strLenght && str[index] >= '0' && str[index] <= '9') {
                        index++;
                    }
                    if (index < strLenght && (str[index] == 'e' || str[index] == 'E')) {
                        return isExponential(str, strLenght, index);
                    }
                } else if (str[index] == 'e' || str[index] == 'E') {
                    return isExponential(str, strLenght, index);
                } else {
                    return false;
                }
            }
            return index == strLenght;
        }
    
        // 判断是否是科学计数法
        public boolean isExponential(char[] str, int strLenght, int index) {
            index++;
            if (index < strLenght && (str[index] == '+' || str[index] == '-')) {
                index++;
            }
            if (index == strLenght) {
                return false;
            }
            while (index < strLenght && str[index] >= '0' && str[index] <= '9') {
                index++;
            }
            return index == strLenght ? true : false;
        }
    }

python:

略

[Link 1]: https://www.nowcoder.com/ta/coding-interviews?page=1
[70]: /images/20220527/4d8f5f37b25e42839014c983536f2690.png