如何从string array中筛选首字符为数字、次字符为字母的元素？

下面是几种主流编程语言的实现方案，核心逻辑均为验证字符串的第一个字符为数字、第二个为字母，同时规避字符串长度不足2的异常情况：

JavaScript 实现 #

方案1：直接字符判断 #

const strArray = ["1a", "b2", "3C", "45", "d6", "z"];
const result = strArray.filter(str => {
  if (str.length < 2) return false;
  const firstChar = str[0];
  const secondChar = str[1];
  return !isNaN(parseInt(firstChar)) && /[a-zA-Z]/.test(secondChar);
});
console.log(result); // 输出: ["1a", "3C"]

方案2：正则表达式匹配 #

用正则/^\d[a-zA-Z]/直接匹配字符串开头的规则，写法更简洁：

const strArray = ["1a", "b2", "3C", "45", "d6", "z"];
const result = strArray.filter(str => /^\d[a-zA-Z]/.test(str));
console.log(result); // 输出: ["1a", "3C"]

Python 实现 #

方案1：循环遍历判断 #

str_array = ["1a", "b2", "3C", "45", "d6", "x"]
result = []
for s in str_array:
    if len(s) >= 2 and s[0].isdigit() and s[1].isalpha():
        result.append(s)
print(result)  # 输出: ['1a', '3C']

方案2：列表推导式简化 #

str_array = ["1a", "b2", "3C", "45", "d6", "x"]
result = [s for s in str_array if len(s)>=2 and s[0].isdigit() and s[1].isalpha()]
print(result)

Java 实现 #

import java.util.ArrayList;
import java.util.List;

public class FilterTargetStrings {
    public static void main(String[] args) {
        String[] strArray = {"1a", "b2", "3C", "45", "d6", "y"};
        List<String> result = new ArrayList<>();
        
        for (String s : strArray) {
            if (s.length() >= 2) {
                char firstChar = s.charAt(0);
                char secondChar = s.charAt(1);
                if (Character.isDigit(firstChar) && Character.isLetter(secondChar)) {
                    result.add(s);
                }
            }
        }
        
        System.out.println(result); // 输出: [1a, 3C]
    }
}

内容的提问来源于stack exchange，提问作者user21387330