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Create 0394-decode-string.js #2615

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12b985e
Create 0394-decode-string.js
aadil42 Jun 21, 2023
c9c15d5
Update 0394-decode-string.js
aadil42 Jul 3, 2023
0c06763
Update 0394-decode-string.js
aadil42 Jul 22, 2023
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34 changes: 34 additions & 0 deletions javascript/0394-decode-string.js
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Original file line number Diff line number Diff line change
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/**
* Stack
* https://leetcode.com/problems/decode-string/
*
* Time O(n) | Space O(n)
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Review these complexities

/**
 * Stack
 * Time O(N * (max(K)^count(K))) | Space O(N * sum((max(K)^count(K))))
 * @param {string} s
 * @return {string}
 */
var decodeString = (s, stack = []) => {
    for (const char of s) {
        const isClosed = (char === ']');
        if (!isClosed) { stack.push(char); continue; }
    
        const string = getString(stack);
        const count = getCount(stack);
        
        repeatWord(string, count, stack);
    }      
    
    return stack.join('');
}

const getString = (stack, word = []) => {
    const isOpen = () => (stack[(stack.length - 1)] === '[')
    while (!isOpen()) {
        word.push(stack.pop());
    }

    stack.pop();/* ] -> */

    return word.reverse();
}

var getCount = (stack, base = 1, count = 0) => {
    while (0 < stack.length) {
        if (isNaN(Number(stack[(stack.length - 1)]))) break;

        count += (getCode(stack.pop()) * base);
        base *= 10;
    }

    return count;
}

var getCode = (char, zero = 48) => (char.charCodeAt(0) - zero);

const repeatWord = (string, count, stack) => {
    while ((0 < count)) {
        stack.push( ...string );
        count -= 1;
    }
}

/**
 * Stack - Node
 * Time O(N * max(K)) | Space O(N + M)
 * @param {string} s
 * @return {string}
 */
var decodeString = (s, count = 0, stack = [], buffer = []) => {
    for (const char of s) {/* Time O(N) */
        if (!isNaN(Number(char))) {
            count *= 10;
            count += getCode(char);

            continue;
        }

        const isOpen = (char === '[');
        if (isOpen) {
            stack.push([ buffer, count ]);
            count = 0;
            buffer = [];

            continue;
        }

        const isClosed = (char === ']');
        if (isClosed) {
            buffer = updateBuffer(stack, buffer);

            continue;
        }

        buffer.push(char);
    }

    return buffer.join('');
}

var getCode = (char, zero = 48) => (char.charCodeAt(0) - zero);

const updateBuffer = (stack, buffer) => {
    const [ string, count ] = stack.pop();
    const repeat = buffer.join('')
        .repeat(count);           

    return [ ...string, repeat ];
}

/**
 * DFS
 * Time O(N * max(K)) | Space O(N)
 * @param {string} s
 * @return {string}
 */
var decodeString = (s, index = [ 0 ], buffer = []) => {
    while (index[0] < s.length) {
        const char = s[index[0]];

        const isBaseCase = (char === ']');
        if (isBaseCase) break;

        if (isAlpha(char, index, buffer)) continue;

        const string = dfsIndOrder(s, index);
        buffer.push(string);
    }

    return buffer.join('');
}

const isAlpha = (char, index, buffer) => {
    if (!isNaN(Number(char))) return false;

    buffer.push(char);
    index[0] += 1;

    return true;
}

const dfsIndOrder = (s, index) => {
    const count = getCount(s, index);

    index[0] += 1; /* [ -> */
    const string = decodeString(s, index);
    index[0] += 1; /* ] -> */

    return string.repeat(count);
}

var getCode = (char, zero = 48) => (char.charCodeAt(0) - zero);

var getCount = (s, index, count = 0) => {
    while (index[0] < s.length) {
        const char = s[index[0]];

        if (isNaN(Number(char))) break;

        count *= 10;
        count += getCode(char);
        index[0] += 1;
    }

    return count;
}

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What is K?

* @param {string} s
* @return {string}
*/
var decodeString = function(s) {
const myStack = [];
let result = '';
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Remove unused variable

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removed result var.


for(let i = 0; i < s.length; i++) {
if(s[i] !== ']') {
myStack.push(s[i]);
continue;
}

let subStr = '';
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Avoid String, use char array instead

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using array now.

while(myStack[myStack.length - 1] !== '[') {
subStr = myStack.pop() + subStr;
}
myStack.pop();

let k = '';
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Avoid string concatination, use char array instead

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using array now.

while(!isNaN(myStack[myStack.length - 1])) {
k = myStack.pop() + k;
}

myStack.push(subStr.repeat(+k));
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Repeat will increase time and space

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Ok, so the new time complexity would be n * (the time it takes to get the number of substrings). The space will be the same right?

}

return myStack.join('');
};