Leetcode(45) Jump Game II

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Description

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:

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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.

解法

贪心算法解题，设置两个指针变量，pre指向前一步跳的最远的点，cur指向这一步跳的最远的点，每一次计算cur时，都通过0到pre中的点选，选择跳的最远的距离。如果pre和cur相等，说明都是0，原地跳，失败。

具体代码如下：

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class Solution {
    public int jump(int[] nums) {
        int pre = 0;
        int cur = 0;
        int end = nums.length - 1;
        int res = 0;
        while (cur < end) {
            res++;
            pre = cur;
            for (int i = 0; i <= pre; i++) {
                cur = Math.max(cur, i + nums[i]);
            }
            if (pre == cur) return -1;
        }
        return res;
    }
}