Validate Stack Sequences

Problem Statement - link #

Given two integer arrays pushed and popped each with distinct values, return true if this could have been the result of a sequence of push and pop operations on an initially empty stack, or false otherwise.

Examples #

Example 1:

Input: pushed = [1,2,3,4,5], popped = [4,5,3,2,1]
Output: true
Explanation: We might do the following sequence:
push(1), push(2), push(3), push(4),
pop() -> 4,
push(5),
pop() -> 5, pop() -> 3, pop() -> 2, pop() -> 1

Example 2:

Input: pushed = [1,2,3,4,5], popped = [4,3,5,1,2]
Output: false
Explanation: 1 cannot be popped before 2.

Example 3:

Input: n = 4
Output: true
Explanation: n is already a perfect square, Alice can win with one move, removing 4 stones (4 -> 0).

Constraints #

• 1 <= pushed.length <= 1000
• 0 <= pushed[i] <= 1000
• All the elements of pushed are unique.
• popped.length == pushed.length
• popped is a permutation of pushed.

Solutions #

class Solution {
public:
    bool winnerSquareGame(int n) {
    vector<int> dp(n+1,0);
        for (int i = 0; i <= n; i++) {
            if (dp[i]) {
                continue;
            }
            for (int k = 1; i + k * k <= n; k++) {
                dp[i + k * k] = true;
            }
        }
        return dp[n];   
    }
};