zoukankan      html  css  js  c++  java
  • Codeforces Round #370 (Div. 2)(简单逻辑,比较水)

    C. Memory and De-Evolution
    time limit per test
    2 seconds
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    Memory is now interested in the de-evolution of objects, specifically triangles. He starts with an equilateral triangle of side length x, and he wishes to perform operations to obtain an equilateral triangle of side length y.

    In a single second, he can modify the length of a single side of the current triangle such that it remains a non-degenerate triangle (triangle of positive area). At any moment of time, the length of each side should be integer.

    What is the minimum number of seconds required for Memory to obtain the equilateral triangle of side length y?

    Input

    The first and only line contains two integers x and y (3 ≤ y < x ≤ 100 000) — the starting and ending equilateral triangle side lengths respectively.

    Output

    Print a single integer — the minimum number of seconds required for Memory to obtain the equilateral triangle of side length y if he starts with the equilateral triangle of side length x.

    Examples
    Input
    6 3
    Output
    4
    Input
    8 5
    Output
    3
    Input
    22 4
    Output
    6
    Note

    In the first sample test, Memory starts with an equilateral triangle of side length 6 and wants one of side length 3. Denote a triangle with sides a, b, and c as (a, b, c). Then, Memory can do .

    In the second sample test, Memory can do .

    In the third sample test, Memory can do:

    .

    题意:

    给出边长为x的等边三角形,每次操作可以将其中一边变成任意长度,但改变后三边仍能构成三角形,问最少几次操作可以变成边长为y的等边三角形;

    思路:

    从y往x反推,用数组a存储当前边的状态,每次让最小边变成最长边,由公理:三角形的最长边小于另两边之和得a[0]=a[1]+a[2]-1;

    注意边界条件x, 即a[0]=min(a[1]+a[2]-1, x);

    代码:

     1 #include <bits/stdc++.h>
     2 #define ll long long
     3 using namespace std;
     4 
     5 int main(void)
     6 {
     7     int x, y;
     8     ll ans=0;
     9     cin >> x >> y;
    10     int a[3];
    11     a[0]=a[1]=a[2]=y;
    12     while(a[0]<x)
    13     {
    14         ans++;
    15         a[0]=min(a[1]+a[2]-1, x);
    16         sort(a, a+3);
    17     }
    18     cout << ans << endl;
    19     return 0;
    20 }



    苦难归于我,荣耀和鲜花也将归于我;     ------ geloutingyu

  • 相关阅读:
    MySql查询当前数据的上一条和下一条的记录
    FastAdmin的基本使用
    ThinkPHP5——安装验证码和使用
    ThinkPHP的模型关联(多对多关联)
    ThinkPHP5——模型关联(一对一关联)
    python之路----递归函数(二分查找法)
    python之路----整理函数知识点(字符编码,文件处理)
    python基础:重要篇 -----基本数据类型和用法
    python基础:网络基础和python基础(变量和程序交互)
    计算机基础系列一:操作系统
  • 原文地址:https://www.cnblogs.com/geloutingyu/p/5861273.html
Copyright © 2011-2022 走看看