find-nested-brackets.js

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(S) {
  if (S == '') return 1;
  
  let stack = [];
  
  // write your code in JavaScript (Node.js 8.9.4)
  for (let i = 0; i < S.length; i++) {
      // console.log(S[i])
      let bracket = S[i];
      if (bracket == '{' || bracket == '(' || bracket == '[') {
        stack.push(bracket);
      } else if (bracket == '}' && stack.length) {
        let popped = stack.pop();
      //   console.log('popped', popped);
        if (popped != '{') return 0;
      } else if (bracket == ']' && stack.length) {
        let popped = stack.pop();
      //   console.log('popped', popped);
        if (popped != '[') return 0;
      } else if (bracket == ')' && stack.length) {
        let popped = stack.pop();
      //   console.log('popped', popped);
        if (popped != '(') return 0;
      }
  }

  // console.log('Stack', stack);

  if (!stack.length) return 1;

  return 0;
  
  
}

/*
A string S consisting of N characters is considered to be properly nested if any of the following conditions is true:

S is empty;
S has the form "(U)" or "[U]" or "{U}" where U is a properly nested string;
S has the form "VW" where V and W are properly nested strings.
For example, the string "{[()()]}" is properly nested but "([)()]" is not.

Write a function:

function solution(S);

that, given a string S consisting of N characters, returns 1 if S is properly nested and 0 otherwise.

For example, given S = "{[()()]}", the function should return 1 and given S = "([)()]", the function should return 0, as explained above.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [0..200,000];
string S consists only of the following characters: "(", "{", "[", "]", "}" and/or ")".
*/