Jump Game II - LeetCode javascript solutions

Problem

Given an array of non-negative integers, you are initially positioned at the first index of the array.

Each element in the array represents your maximum jump length at that position.

Your goal is to reach the last index in the minimum number of jumps.

Example:

Input: [2,3,1,1,4]
Output: 2
Explanation: The minimum number of jumps to reach the last index is 2.
    Jump 1 step from index 0 to 1, then 3 steps to the last index.

Note:

You can assume that you can always reach the last index.

Solution

/**
 * @param {number[]} nums
 * @return {number}
 */
var jump = function(nums) {
  var len = nums.length;
  var step = 0;
  var now = 0;
  var max = 0;

  for (var i = 0; i < len - 1; i++) {
    max = Math.max(max, i + nums[i]);
    if (i === now) {
      step++;
      now = max;
    }
  }

  return step;
};

Explain:

假设 nums[0] === 8，那就是 1 ~ 8 都只需一步就能到达

在 1 ~ 8 里找出跳得最远的，假设能跳到 12，那就是 9 ~ 12 都只需要两步就能到达

在 9 ~ 12 里找出跳得最远的…

贪心，每次选最好的.

Complexity:

Time complexity : O(n).
Space complexity : O(1).