Next Greater Element of a Linked List - Amazon Top Interview Questions


Problem Statement :


Given a singly linked list node, replace every node's value with the first greater node's value to its right. If a node doesn't have a next greater node, set its value to 0.

Constraints

n ≤ 100,000 where n is the number of nodes in node

Example 1

Input

node = [3, 2, 4, 5]

Output

[4, 4, 5, 0]

Example 2

Input

node = [1, 1, 1, 1]

Output

[0, 0, 0, 0]


Solution :



title-img 




                        Solution in C++ :

void replace(LLNode* root, stack<int>& s) {
    if (root == NULL) return;
    replace(root->next, s);
    while (!s.empty() and s.top() <= root->val) s.pop();
    int vals = root->val;
    root->val = s.empty() ? 0 : s.top();
    s.push(vals);
}
LLNode* solve(LLNode* node) {
    stack<int> s;
    replace(node, s);
    return node;
}
                    




                        Solution in Python : 
                            
class Solution:
    def solve(self, node):
        stack = []
        ans = node
        while node:
            while stack and node.val > stack[-1].val:
                top = stack.pop()
                top.val = node.val
            stack.append(node)
            node = node.next

        for el in stack:
            el.val = 0

        return ans


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