leetcode:Jump Game

最新推荐文章于 2020-02-24 08:15:00 发布

原创最新推荐文章于 2020-02-24 08:15:00 发布 · 470 阅读

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本文探讨了如何通过数组元素代表的最大跳跃长度来判断是否能从数组起始位置跳到末尾，采用贪心算法进行路径优化。通过实例演示算法应用，深入理解跳跃游戏策略。

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 canJumpInternal(int A[], int n, int tryingPos)
    {
        if (tryingPos >= n-1)
            return true;

        //current position value
        int val = A[tryingPos];
        
        if (val == 0)
        {
            return false;
        }
        
        //greedy algorithm
        int maxJumPos = tryingPos;
        for (int i=1; i<=val; i++)
        {
            int nextJumPos = tryingPos+i+A[tryingPos+i];
            
            // here we try to get the maxJumpPos from current position
            if (nextJumPos<n && nextJumPos>maxJumPos)
            {
                maxJumPos = nextJumPos;
            }
            else if (nextJumPos >= n-1)
            {
                return true;
            }
        }
        
        if (maxJumPos == tryingPos)
            return false;
            
        return canJumpInternal(A, n, maxJumPos);
    }
    
    bool canJump(int A[], int n) {
        
        if (A == NULL || n == 0)
            return false;
            
        if (n == 1)
            return true;
        
        //recursive: this is the key point of this solution
        return canJumpInternal(A, n, 0);
    }
};