Task description: Determine whether a given string of parentheses (multiple types) is properly nested. More details are given below.
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 “)”.
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Solution for Determine whether a given string of parentheses (multiple types) is properly nested
function solution(S) {
// write your code in JavaScript (Node.js 4.0.0)
var i = 0;
var stack = [];
if(S.length % 2 === 1) {
return 0;
}
for(i=0; i<S.length; i++) {
var char = S.charAt(i);
if(isOpener(char)) {
stack.push(char);
} else {
if(stack.length === 0) {
return 0;
} else {
var lastChar = stack.pop();
if(!checkCloser(lastChar, char)) {
return 0;
}
}
}
}
if(stack.length === 0) {
return 1;
} else {
return 0;
}
}
function isOpener(char) {
return char === '{' || char === '[' || char === '(' ? true : false;
}
function checkCloser(opener, closer) {
if(opener === '(' && closer === ')') return true;
if(opener === '[' && closer === ']') return true;
if(opener === '{' && closer === '}') return true;
return false;
}
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