Jump Game

LeetCode #55 — Medium

You are given an integer array nums. You are initially positioned at the array's first index, and each element in the array represents your maximum jump length at that position.

Return true if you can reach the last index, or false otherwise.

Examples

Example 1

Input:  nums = [2, 3, 1, 1, 4]
Output: true
Explanation: Jump 1 step from index 0 to 1, then 3 steps to the last index.

Example 2

Input:  nums = [3, 2, 1, 0, 4]
Output: false
Explanation: You will always arrive at index 3 no matter what. Its maximum jump length is 0,
             which makes it impossible to reach the last index.

Constraints

• 1 <= nums.length <= 10^4
• 0 <= nums[i] <= 10^5

What to practise

• Greedy: track the furthest index reachable so far. Iterate through the array; at each i, if i > furthest, return false. Otherwise update furthest = max(furthest, i + nums[i]).
• Stop early if furthest >= len(nums) - 1.
• Why is greedy correct? At each position you have full information about reach; locally extending the max can never hurt.