Question

我正在尝试为OR运算符的操作数添加括号。例如，如果我有如下声明，

C>O AND C>4 OR C>0 AND C>5

我想将其格式化如下

(C>O AND C>4) OR (C>0 AND C>5)

我写了一个简单的代码，如下所示。但是，如果字符串具有多个OR语句，则代码无法正常工作。我被告知正则表达式可以实现这一点。但是我对正则表达式的了解非常少。

string mystring = "C>O AND C>4 OR C>0 AND C>5";
int indexFound = mystring.IndexOf("OR");
string left = mystring.Substring(0, indexFound - 1);
string right = mystring.Substring(indexFound + 2, mystring.Length - (indexFound + 2));
string output = "(" + left + ")" + "OR" + "(" + right + ")";

任何帮助都将不胜感激。

Answer 1

这是通过正则表达式的方式：

static string AddBracketsToOr(string input)
{            
    Regex regex = new Regex(@"(?<left>.+[AND|OR].+) OR (?<right>.+[AND|OR].+)");
    Match match = regex.Match(input);

    if (match == null)
        throw new Exception("Wrong input format");

    return String.Format("({0}) OR ({1})", 
                         match.Groups["left"], match.Groups["right"]);
}

用法：

var result = AddBracketsToOr("C>O AND C>4 OR C>0 AND C>5");

更新：适用于

"C>O AND C>4 OR C>0 AND C>5" // (C>O AND C>4) OR (C>0 AND C>5)
"C>9 OR C>O AND C>4 OR C>0 AND C>5" // (C>9 OR C>O AND C>4) OR (C>0 AND C>5)
"C>9 OR C>O OR C>0 AND C>5" // (C>9 OR C>O) OR (C>0 AND C>5)

Answer 2

目前您的代码中没有使用任何正则表达式。

.Substring()方法会在OR内找到第一个mystring并将其拆分为left和right个子字符串。因此，只能按照您描述的方式处理第一个OR。

您必须在mystring上创建一个循环，直到找不到OR的出现为止。

示例代码

string mystring = "C>O AND C>4 OR C>0 AND C>5";
string output = "";

int indexFound = mystring.IndexOf("OR");

// indexOf returns -1 if the string cannot be found.
// We quit our loop once -1 is returned.
while (indexFound > -1)
{
    // Compute the "left" side of our current mystring.
    string left = mystring.Substring(0, indexFound - 1);

    // And then append it to our final output variable.
    output += "(" + left + ")" + "OR";

    // Instead of directly adding the "right" side, we
    // "shorten" mystring to only contain the right side.
    // This effectively "skips" over the "left" and "OR"
    // and will allow us to process the remaining "OR"s.
    mystring = mystring.Substring(indexFound + 2)

    // Finally, we update indexFound to check if there
    // are any more "OR"s inside our mystring.
    indexFound = mystring.IndexOf("OR");
}

// Before returning, we add the remaining mystring to
// our output.  You have to decide whether you want
// to add the parentheses here.
output += "(" + mystring + ")";

希望有所帮助。

字符串中的布尔运算符

2 个答案: