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📜  如何使用正则表达式验证十六进制颜色代码

📅  最后修改于: 2021-05-06 21:44:58             🧑  作者: Mango

给定字符串str ,任务是使用正则表达式检查字符串是否为有效的十六进制颜色代码。

例如:#abc,#ABC,#000,#FFF,#000000,#FF0000,#00FF00,#0000FF,#FFFFFF都是有效的十六进制颜色代码。
例子:

方法:可以使用正则表达式解决此问题。

  • 获取字符串。
  • 创建一个正则表达式来检查有效的十六进制颜色代码,如下所述:
regex = "^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$";
  • 在哪里:
    • ^表示字符串的开头。
    • 代表十六进制颜色代码,必须以“#”符号开头。
    • (代表群组的开始。
    • [A-Fa-f0-9] {6}代表af,AF的字母或0-9的数字,长度为6。
    • |代表or。
    • [A-Fa-f0-9] {3}表示af,AF或0-9的数字,长度为3。
    • )代表组的结尾。
    • $表示字符串的结尾。
  • 在Java,使用regex匹配给定的字符串,这可以通过使用Pattern.matcher()来完成。
  • 如果字符串与给定的正则表达式匹配,则返回true;否则返回false。

下面是上述方法的实现:

C++
// C++ program to validate the
// hexadecimal color code using Regular Expression
#include 
#include 
using namespace std;
 
// Function to validate the hexadecimal color code.
bool isValidHexaCode(string str)
{
 
  // Regex to check valid hexadecimal color code.
  const regex pattern("^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$");
 
  // If the hexadecimal color code
  // is empty return false
  if (str.empty())
  {
     return false;
  }
 
  // Return true if the hexadecimal color code
  // matched the ReGex
  if(regex_match(str, pattern))
  {
    return true;
  }
  else
  {
    return false;
  }
}
 
// Driver Code
int main()
{
   
  // Test Case 1:
  string str1 = "#1AFFa1";
  cout << str1 + ": " << isValidHexaCode(str1) << endl;
 
  // Test Case 2:
  string str2 = "#F00";
  cout << str2 + ": " <<  isValidHexaCode(str2) << endl;
 
  // Test Case 3:
  string str3 = "123456";
  cout << str3 + ": " <<  isValidHexaCode(str3) << endl;
 
  // Test Case 4:
  string str4 = "#123abce";
  cout << str4 + ": " <<  isValidHexaCode(str4) << endl;
 
  // Test Case 5:
  string str5 = "#afafah";
  cout << str5 + ": " <<  isValidHexaCode(str5) << endl;
 
  return 0;
}
 
// This code is contributed by yuvraj_chandra


Java
// Java program to validate hexadecimal
// colour code using Regular Expression
 
import java.util.regex.*;
 
class GFG {
 
    // Function to validate hexadecimal color code .
    public static boolean isValidHexaCode(String str)
    {
        // Regex to check valid hexadecimal color code.
        String regex = "^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$";
 
        // Compile the ReGex
        Pattern p = Pattern.compile(regex);
 
        // If the string is empty
        // return false
        if (str == null) {
            return false;
        }
 
        // Pattern class contains matcher() method
        // to find matching between given string
        // and regular expression.
        Matcher m = p.matcher(str);
 
        // Return if the string
        // matched the ReGex
        return m.matches();
    }
 
    // Driver Code.
    public static void main(String args[])
    {
 
        // Test Case 1:
        String str1 = "#1AFFa1";
        System.out.println(
            str1 + ": "
            + isValidHexaCode(str1));
 
        // Test Case 2:
        String str2 = "#F00";
        System.out.println(
            str2 + ": "
            + isValidHexaCode(str2));
 
        // Test Case 3:
        String str3 = "123456";
        System.out.println(
            str3 + ": "
            + isValidHexaCode(str3));
 
        // Test Case 4:
        String str4 = "#123abce";
        System.out.println(
            str4 + ": "
            + isValidHexaCode(str4));
 
        // Test Case 5:
        String str5 = "#afafah";
        System.out.println(
            str5 + ": "
            + isValidHexaCode(str5));
    }
}


Python3
# Python3 program to validate
# hexadecimal colour code using
# Regular Expression
import re
 
# Function to validate
# hexadecimal color code .
def isValidHexaCode(str):
 
    # Regex to check valid
    # hexadecimal color code.
    regex = "^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$"
 
    # Compile the ReGex
    p = re.compile(regex)
 
    # If the string is empty
    # return false
    if(str == None):
        return False
 
    # Return if the string
    # matched the ReGex
    if(re.search(p, str)):
        return True
    else:
        return False
 
# Driver Code.
 
# Test Case 1:
str1 = "#1AFFa1"
print(str1, ":", isValidHexaCode(str1))
 
# Test Case 2:
str2 = "#F00"
print(str2, ":", isValidHexaCode(str2))
 
# Test Case 3:
str3 = "123456"
print(str3, ":", isValidHexaCode(str3))
 
# Test Case 4:
str4 = "#123abce"
print(str4, ":", isValidHexaCode(str4))
 
# Test Case 5:
str5 = "#afafah"
print(str5, ":", isValidHexaCode(str5))
 
# This code is contributed by avanitrachhadiya2155


输出:
#1AFFa1: true
#F00: true
123456: false
#123abce: false
#afafah: false