Solution: Next Greater Element I

Explore an optimized approach to solving the Next Greater Element problem by using a hash map and monotonic stack. Understand how storing elements of an array and their next greater counterparts in a hash map helps streamline finding results for a subset array. Learn to implement this efficient solution that improves time complexity from O(n1×n2) to O(n), and master the space-time trade-offs in algorithm design.

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Statement
Solution
- Naive approach
- Optimized approach using hash map

Statement

Given the two distinct integer arrays, nums1 and nums2, where nums1 is a subset of nums2, find all the next greater elements for nums1 values in the corresponding places of nums2.

In general, the next greater element of an element, $x$ , in an array is the first greater element present on the right side of $x$ in the same array. However, in the context of this problem, for each element $x$ in nums1, find the next greater element present on the right side of $x$ in nums2 and store it in the ans array. If there is no such element, store ...