zoukankan      html  css  js  c++  java
  • 877. Stone Game

    package LeetCode_877
    
    /**
     * 877. Stone Game
     * https://leetcode.com/problems/stone-game/description/
     *
     * Alex and Lee play a game with piles of stones.
     * There are an even number of piles arranged in a row, and each pile has a positive integer number of stones piles[i].
    The objective of the game is to end with the most stones.
    The total number of stones is odd, so there are no ties.
    Alex and Lee take turns, with Alex starting first.
    Each turn, a player takes the entire pile of stones from either the beginning or the end of the row.
    This continues until there are no more piles left, at which point the person with the most stones wins.
    Assuming Alex and Lee play optimally, return True if and only if Alex wins the game.
    
    Example 1:
    Input: piles = [5,3,4,5]
    Output: true
    Explanation:
    Alex starts first, and can only take the first 5 or the last 5.
    Say he takes the first 5, so that the row becomes [3, 4, 5].
    If Lee takes 3, then the board is [4, 5], and Alex takes 5 to win with 10 points.
    If Lee takes the last 5, then the board is [3, 4], and Alex takes 4 to win with 9 points.
    This demonstrated that taking the first 5 was a winning move for Alex, so we return true.
    
    Constraints:
    2 <= piles.length <= 500
    piles.length is even.
    1 <= piles[i] <= 500
    sum(piles) is odd.
     * */
    class Solution {
        /*
        * solution: Min-Max + DP(Top-Down), Time complexity:O(n^2), Space complexity:O(n^2)
        * */
        fun stoneGame(piles: IntArray): Boolean {
            val dp = Array(piles.size) { IntArray(piles.size) }
            //the winner is the score>0
            return getScore(piles, 0, piles.size - 1, dp) > 0
        }
    
        private fun getScore(piles: IntArray, left: Int, right: Int, dp: Array<IntArray>): Int {
            if (left == right) {
                return piles[left]
            }
            if (dp[left][right] > 0) {
                return dp[left][right]
            }
            //left and right both try to get the larger score
            val score = Math.max(
                piles[left] - getScore(piles, left + 1, right, dp),
                piles[right] - getScore(piles, left, right - 1, dp)
            )
            dp[left][right] = score
            return score
        }
    }
  • 相关阅读:
    对Request.Url片段解析
    Php学习之路四
    解析bmp图像(某年全国软件大赛题目)
    工信部软件大赛(解析bmp)
    Php学习之路三(字符串操作)
    C++二维数组做形参
    php学习之路五(表单验证)
    PHP(学习之路一)
    PHp学习之路二(数组练习)
    解析网页(KMP算法实现部分)
  • 原文地址:https://www.cnblogs.com/johnnyzhao/p/13629922.html
Copyright © 2011-2022 走看看