55. Jump Game 🏃‍♂️

Difficulty: Medium - Tags: Array, Greedy, Dynamic Programming

Description

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.

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Solution 💡

The time complexity is $O(n)$, and the space complexity is $O(1)$, where $n$ is the number of elements in the array.

Java

class Solution {
    public boolean canJump(int[] nums) {
        int maxReach = 0;
        for (int i = 0; i < nums.length; i++) {
            if (i > maxReach) return false;
            maxReach = Math.max(maxReach, i + nums[i]);
        }
        return true;
    }
}

You can find the full Solution.java file here.