55. Jump Game

Leetcode

https://leetcode.com/problems/jump-game/description/

題目

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.

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.

解答

方法一

紀錄目前最大可以走到的位置 (max)，接著每走一步都去更新 max，當走到的 index > max 時，就代表這個地方走不到

var canJump = function (nums) {
    let max = 0;

    for (let i = 0; i < nums.length; i++) {
        // 走不到
        if (i > max) {
            return false;
        }

        const value = nums[i];
        max = Math.max(max, i + value);
        // max 大於總長度 => 走得到終點
        if (max >= nums.length - 1) {
            return true;
        }
    }

    return true;
};