如何解决这个“解析和平衡尖括号”的问题？ （JavaScript）

Question

我正在努力解决遇到的算法问题（失败了）。现在，我试图了解如何解决该问题。

  

问题：   给定一串尖括号，编写一个函数，在字符串的开头和结尾添加括号以使所有括号匹配。如果每个<都有对应的>，并且每个>都有对应的<。

，则尖括号匹配。      

示例输入字符串：> <<> << / p>      

输出字符串为<> <<> <>>

---

我的主要问题是如何处理输入字符串中的多个<字符，例如<<。根据给出的示例，我最终会得到一些嵌套的尖括号，但是我目前无法弄清楚该如何做。

我可以解决示例输入，但是当我给它其他输入时，输出并不总是我所期望的（输入2和输入6）。帮助将不胜感激。

const process = (strInput) => {

  let strOutput = [];
  let stack = [];
  let popped ='';

  for (let i = 0; i < strInput.length; i++) {

    if (strInput[i] === '>') {
      if (stack[stack.length - 1] === '<') {
        popped = stack.pop();
        strOutput.push(popped);
        strOutput.push(strInput[i]);
      } else {
        strOutput.push('<');
        strOutput.push(strInput[i]);
      }
    } else {
        if (stack[stack.length - 1] === '<') {
            strOutput.push('<');
            stack.push(strInput[i]);
        } else {
            stack.push(strInput[i]);
        }

    }   
  }

// After string has been read, check the stack for <

  for (let i = 0; i < stack.length; i++) {
    strOutput.push('>');
  }



  return strOutput.join('');
};

let result = '';

console.log('Input 1: ><<><');

result = process('><<><');

console.log('Output 1: ' + result);
console.log('Expected Output 1: ' + '<><<><>>');

console.log('Input 2: <><<');

result = process('<><<');

console.log('Output 2: ' + result);

console.log('Expected Output 2: ' + '<><<>>');

console.log('Input 3: <><<<>');

result = process('<><<<>');

console.log('Output 3: ' + result);

console.log('Expected Output 3: ' + '<><<<>>>');

console.log('Input 4: <><<<><');

result = process('<><<<><');

console.log('Output 4: ' + result);

console.log('Expected Output 4: ' + '<><<<><>>>');

console.log('Input 5: ><<>');

result = process('><<>');

console.log('Output 5: ' + result);

console.log('Expected Output 5: ' + '<><<>>');

console.log('Input 6: ><<<');

result = process('><<<');

console.log('Output 6: ' + result);

console.log('Expected Output 6: ' + '<><<<>>>');

console.log('Input 7: >>>');

result = process('>>>');

console.log('Output 7: ' + result);

console.log('Expected Output 7: ' + '<<<>>>');

Answer 1

为简化操作，而不是使用堆栈数组，请考虑仅使用 一个数字：到目前为止，打开的<标签的数量。遇到>时，如果没有当前的打开标记，则在字符串的开头添加<（同时将打开标记计数保持为0）。然后，最后添加与当前打开的标签数匹配的>个数：

const process = (str) => {
  let openCount = 0;
  let additionalLeadingOpenTags = 0;
  for (const char of str) {
    if (char === '>') {
      if (openCount === 0) {
        additionalLeadingOpenTags++;
      } else {
        openCount--;
      }
    } else {
      openCount++;
    }
  }
  return '<'.repeat(additionalLeadingOpenTags) + str + '>'.repeat(openCount);
};

console.log('Input 1: ><<><');

result = process('><<><');

console.log('Output 1: ' + result);
console.log('Expected Output 1: ' + '<><<><>>');

console.log('Input 2: <><<');

result = process('<><<');

console.log('Output 2: ' + result);

console.log('Expected Output 2: ' + '<><<>>');

console.log('Input 3: <><<<>');

result = process('<><<<>');

console.log('Output 3: ' + result);

console.log('Expected Output 3: ' + '<><<<>>>');

console.log('Input 4: <><<<><');

result = process('<><<<><');

console.log('Output 4: ' + result);

console.log('Expected Output 4: ' + '<><<<><>>>');

console.log('Input 5: ><<>');

result = process('><<>');

console.log('Output 5: ' + result);

console.log('Expected Output 5: ' + '<><<>>');

console.log('Input 6: ><<<');

result = process('><<<');

console.log('Output 6: ' + result);

console.log('Expected Output 6: ' + '<><<<>>>');

Answer 2

快速版本

帮助参考

//  Input: "><<><"
//  Output: "<><<><>>"

class Angles {

func addAngles(angles: String) -> String {

var openingCount = 0
var leadingOpenCounts = 0
var newAngles = ""

newAngles = angles

print("New angles \(newAngles)")

for c in newAngles {


    print("Char = \(String(c) )")

    if String(c) == ">" {

        if openingCount == 0 {
            leadingOpenCounts = leadingOpenCounts + 1
        }
        else {
            openingCount = openingCount - 1
        }

    }
    if String(c) == "<" {
        openingCount = openingCount + 1
    }

}

print("LeadingOpenCounts ***** = \(leadingOpenCounts)")
print("OpeningCount ***** = \(openingCount)")
print("Required Closing Count ***** = \(openingCount)")

for _ in 0..<leadingOpenCounts {

    newAngles = "<" + newAngles
}

for _ in 0..<openingCount {
    newAngles.append(">")
}

print(newAngles)
return newAngles
}

}

let angles = Angles()
//><<><
// ><<<>>>
angles.addAngles(angles: "><<><")