Trying to solve a problem at LeetCode called "Valid Parentheses".
Conditions are:
Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
An input string is valid if:
Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order.
I wrote a function and it's working in this snippet:
let arr = ['()']
var isValid = function (data) {
let stack = [];
const bracketsArray = {
'{':'}',
'[':']',
'(':')'
}
for (i=0; i < data[0].length; i++) {
if (data[0][i] == '{' || data[0][i] == '(' || data[0][i] == '[') {
stack.push(data[0][i]);
} else if (data[0][i] == '}' || data[0][i] == ']' || data[0][i] == ')') {
if (bracketsArray[stack[stack.length-1]] == data[0][i]) {
stack.pop()
}
}
}
if (stack.length == 0) {
return true
} else {
return false
}
}
console.log(isValid(arr))Function gives a correct output (boolean) But when I run this code at LeetCode for some reason the same code gives me a wrong boolean.
Don't understand what is wrong.
/**
* @param {string} s
* @return {boolean}
*/
var isValid = function(s) {
let stack = [];
const bracketsArray = {
'{':'}',
'[':']',
'(':')'
}
for (i=0; i < s[0].length; i++) {
if (s[0][i] == '{' || s[0][i] == '(' || s[0][i] == '[') {
stack.push(s[0][i]);
} else if (s[0][i] == '}' || s[0][i] == ']' || s[0][i] == ')') {
if (bracketsArray[stack[stack.length-1]] == s[0][i]) {
stack.pop()
}
}
}
if (stack.length == 0) {
return true;
} else {
return false;
}
};Any advice?
On LeetCode the function parameter is a string, but in your tests you are passing an array, and also your function code expects an array, since it accesses the string with s[0], instead of s.
Unrelated, but:
Your code fails when the input is just a closing bracket. This is because your loop doesn't break with return false when a non-matching closing bracket is encountered. This should happen in the else part of if (bracketsArray[stack[stack.length-1]] == s[i]) {
Don't use an undeclared variable i, which will then implicitly become a global variable (if running in non-strict mode).
Don't name your variable bracketsArray since it is not an array.
Make more use of that object, instead of making three comparisons with opening brackets.
The final if...then is overkill for just returning the value of a boolean expression.
So:
var isValid = function(s) {
const stack = [];
const brackets = {
'{':'}',
'[':']',
'(':')'
}
const closing = Object.values(brackets);
for (let ch of s) {
if (brackets[ch]) {
stack.push(brackets[ch]);
} else if (ch == stack.at(-1)) {
stack.pop()
} else if (closing.includes(ch)) {
return false;
}
}
return !stack.length;
};
console.log(isValid("{([])}")); // true
console.log(isValid("]")); // falseThe way you are accessing the current character of the iteration is wrong. Instead of doing s[0][i], simply do s[i].
s[0][i] accesses the first character, and then attempts to get the i-th entry from it (which is undefined).
var isValid = function(s) {
let stack = [];
const bracketsArray = {
'{':'}',
'[':']',
'(':')'
}
for (i=0; i < s.length; i++) {
if (s[i] == '{' || s[i] == '(' || s[i] == '[') {
stack.push(s[i]);
} else if (s[i] == '}' || s[i] == ']' || s[i] == ')') {
if (bracketsArray[stack[stack.length-1]] == s[i]) {
stack.pop()
}
}
}
if (stack.length == 0) {
return true;
} else {
return false;
}
};
isValid("{([])}") // true
isValid("{([)}") // false