Brackets.md

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.

Assume that:

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

Complexity:

• expected worst-case time complexity is O(N);
• expected worst-case space complexity is O(N) (not counting the storage required for input arguments).

function solution(S) {
    var brackets = {
        "{": "}",
        "(": ")",
        "[": "]"
    }

    var closedBrackets = ["}", ")", "]"]
    
    var stack = [];
    
    for (var i =0; i < S.length; i++) {
        if (brackets.hasOwnProperty(S[i])) {
            stack.push(S[i])
        } else if (brackets[stack[stack.length -1]] == S[i]) {
            stack.pop()
        } else if (closedBrackets.indexOf(S[i]) !== -1) {
        	return 0
        }
    }
    
    return stack.length === 0 ? 1 : 0
}