随笔分类 - 数学---数学期望，概率
摘要：pro：给定N*M的矩阵，以及初始玩家位置。 规定玩家每次会等概率的向左走，向右走，向下走，原地不动，问走到最后一行的期望。保留4位小数。 sol：可以列出方程，高斯消元即可，发现是三角矩阵，O(N*M) 元素个数。 也可以用反复逼近答案。 反复做，dp[i][j]=(dp[i][j+1]+dp[i
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摘要：Valera is a coder. Recently he wrote a funny program. The pseudo code for this program is given below: Now Valera wonders: given the values x, k and p
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摘要：A .Assignments 题意：给定距离D，以及N个飞机的速度Vi，单位时间耗油量Fi，总油量Ci。问有多少飞机可以到达目的地。 思路：即问多少飞机满足(Ci/Fi)*Vi>=D > Ci*Vi>=Fi*D; #include<bits/stdc++.h> #define ll long lon
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摘要：5091: [Lydsy1711月赛]摘苹果 Description 小Q的工作是采摘花园里的苹果。在花园中有n棵苹果树以及m条双向道路，苹果树编号依次为1到n，每条道路的两 端连接着两棵不同的苹果树。假设第i棵苹果树连接着d_i条道路。小Q将会按照以下方式去采摘苹果： 1.小Q随机移动到一棵苹果树
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摘要：Description 小Q同学现在沉迷炉石传说不能自拔。他发现一张名为克苏恩的牌很不公平。如果你不玩炉石传说，不必担心，小Q 同学会告诉你所有相关的细节。炉石传说是这样的一个游戏，每个玩家拥有一个 30 点血量的英雄，并且可以用牌 召唤至多 7 个随从帮助玩家攻击对手，其中每个随从也拥有自己的血量
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摘要：In your childhood, do you crazy for collecting the beautiful cards in the snacks? They said that, for example, if you collect all the 108 people in th
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摘要：Description osu 是一款群众喜闻乐见的休闲软件。 我们可以把osu的规则简化与改编成以下的样子: 一共有n次操作，每次操作只有成功与失败之分，成功对应1，失败对应0，n次操作对应为1个长度为n的01串。在这个串中连续的 X个1可以贡献X^3 的分数，这x个1不能被其他连续的1所包含（也
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摘要：Allen and Bessie are playing a simple number game. They both know a function f:{0,1}n→Rf:{0,1}n→R, i. e. the function takes nn binary arguments and re
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摘要：There is a robot on the 2D plane. Robot initially standing on the position (0, 0). Robot can make a 4 different moves: After moving N times Robot gets
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摘要：Given an array of N integers A1, A2, A3…AN. If you randomly choose two indexes i ,j such that 1 ≤ i < j ≤ N, what is the expected value of Ai | Aj? In
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摘要：描述 一日，崔克茜来到小马镇表演魔法。 其中有一个节目是开锁咒：舞台上有 n 个盒子，每个盒子中有一把钥匙，对于每个盒子而言有且仅有一把钥匙能打开它。初始时，崔克茜将会随机地选择 k 个盒子用魔法将它们打开。崔克茜想知道最后所有盒子都被打开的概率，你能帮助她回答这个问题吗？ 输入 第一行一个整数 T
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摘要：数学期望 P=Σ每一种状态*对应的概率。 因为不可能枚举完所有的状态，有时也不可能枚举完，比如抛硬币，有可能一直是正面，etc。在没有接触数学期望时看到数学期望的题可能会觉得很阔怕（因为我高中就是这么认为的，对不起何老板了QwQ），避之不及。 但是现在发现大多数题就是手动找公式或者DP推出即可，只要
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摘要：Organizing a programming contest is not an easy job. To avoid making the problems too difficult, the organizer usually expect the contest result satis
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摘要：King Arthur is an narcissist who intends to spare no coins to celebrate his coming K-th birthday. The luxurious celebration will start on his birthday
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摘要：495. Kids and Prizes Time limit per test: 0.25 second(s) Memory limit: 262144 kilobytes input: standard output: standard ICPC (International Cardboard
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摘要：The dragon and the princess are arguing about what to do on the New Year's Eve. The dragon suggests flying to the mountains to watch fairies dancing i
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摘要：BuggyD loves to carry his favorite die around. Perhaps you wonder why it's his favorite? Well, his die is magical and can be transformed into an N-sid
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摘要：There is a very simple and interesting one-person game. You have 3 dice, namely Die1, Die2 and Die3. Die1 has K1 faces. Die2 has K2 faces. Die3 has K3
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摘要：In 0th day, there are n-1 people and 1 bloodsucker. Every day, two and only two of them meet. Nothing will happen if they are of the same species, tha
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摘要：Akemi Homura is a Mahou Shoujo (Puella Magi/Magical Girl). Homura wants to help her friend Madoka save the world. But because of the plot of the Boss
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