Solve cache, grid path, and substring problems

You are given three independent coding tasks. ## 1) Bounded cache with eviction Design a data structure that stores key–value pairs with a fixed capacity and supports: - `get(key) -> value`: - Return the value if `key` exists, otherwise return `-1`. - Mark the key as **most recently used**. - `put(key, value)`: - Insert or update the value. - Mark the key as **most recently used**. - If inserting causes the number of keys to exceed `capacity`, evict exactly one key: the **least recently used** key. **Requirements** - Aim for **O(1)** average time per operation. **Constraints (typical)** - `1 <= capacity <= 10^5` - Up to `10^5` operations. ## 2) Maximize the minimum value on a grid path You are given an `m x n` integer grid `grid`. A path starts at `(0,0)` and ends at `(m-1,n-1)`, moving only in 4 directions (up/down/left/right) within bounds. Define the **score** of a path as the **minimum** value among all cells on the path. Return the **maximum possible score** among all valid paths. **Constraints (typical)** - `1 <= m, n <= 100` - Cell values are integers within a reasonable range (e.g., `0..10^9`). ## 3) Longest substring without repeating characters Given a string `s`, return the length of the longest contiguous substring that contains **no repeated characters**. **Constraints (typical)** - `0 <= |s| <= 10^5` - `s` may contain ASCII/Unicode characters (clarify with interviewer if needed).