Coding Challenge Practice - Question 61

The task is to determine the validity of a pair of parentheses, brackets or braces

function validate(str) {
  // your code here
}

Use a stack to keep track of opening symbols

const stack = [];
  const pairs = {
    ")":"(",
    "]": "[",
    "}": "{"
  }

Each time you see an opening bracket, brace or parenthesis, push it into the stack

for (let char of str) {
    if(char === "(" || char === "[" || char === "{") {
      stack.push(char); 
    }
}

Each time you see a closing bracket, brace or parenthesis, check if the top of the stack matches

else if ( char === ")" || char === "]" || char === "}") {
      if(stack.pop() !== pairs[char]) {
        return false;
      }
    }

If the stack is empty at the end, the string is valid

return stack.length === 0

The final code

function validate(str) {
  // your code here
  const stack = [];
  const pairs = {
    ")":"(",
    "]": "[",
    "}": "{"
  }
  for (let char of str) {
    if(char === "(" || char === "[" || char === "{") {
      stack.push(char); 
    } else if ( char === ")" || char === "]" || char === "}") {
      if(stack.pop() !== pairs[char]) {
        return false;
      }
    }
  }
  return stack.length === 0;
}

That's all folks!