【leetcode】Jump Game I & II

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.

Determine if you are able to reach the last index.

For example:
A = [2,3,1,1,4], return true.

A = [3,2,1,0,4], return false.

 

class Solution {
public:
    bool canJump(vector<int>& nums) {
        if(nums.size()==0||nums.size()==1) return true;

        int maxstep=nums[0];

        for(int i=1;i<nums.size();i++)
        {
            if(maxstep==0) return false;

            maxstep--;
            if(maxstep<nums[i])
                maxstep=nums[i];

            if(maxstep+i>=nums.size()-1) return true;
        }
    }
};

 

 

II：

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.

For example:
Given array A = [2,3,1,1,4]

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.)

 

class Solution {
public:
    int jump(vector<int>& nums) {
        int result=0;

        int last=0;

        int cur=0;

        for(int i=0;i<nums.size();i++)
        {
            if(i>last)
            {
                last=cur;
                result++;
            }
            cur=max(cur,i+nums[i]);
        }

        return result;
    }
};