# LeetCode: Validate Stack Sequences Solution

## Approach

Push value to stack

Along with that, keep pop stack if its top is equal to the first element of the popped array (also shift the popped array in that case)

## Implementation

1function Stack() {2 const stack = []34 this.push = function (el) {5 stack.push(el)6 }78 this.pop = function () {9 return stack.pop()10 }1112 this.peek = function () {13 return stack[stack.length - 1]14 }1516 this.isEmpty = function () {17 return stack.length === 018 }19}2021/**22 * @param {number[]} pushed23 * @param {number[]} popped24 * @return {boolean}25 */26var validateStackSequences = function (pushed, popped) {27 const N = pushed.length28 const stack = new Stack()29 let i = 030 let j = 031 while (i < N) {32 stack.push(pushed[i++])33 while (stack.peek() === popped[j] && j < N) {34 stack.pop()35 j++36 }37 }3839 return stack.isEmpty()40}

## Comments

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## Tags

leetcode

stack

greedy

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