zoukankan      html  css  js  c++  java
  • poj 2115 C Looooops 扩展欧几里德

    C Looooops
    Time Limit: 1000MS   Memory Limit: 65536K
    Total Submissions: 23616   Accepted: 6517

    Description

    A Compiler Mystery: We are given a C-language style for loop of type
    for (variable = A; variable != B; variable += C)
    
    statement;

    I.e., a loop which starts by setting variable to value A and while variable is not equal to B, repeats statement followed by increasing the variable by C. We want to know how many times does the statement get executed for particular values of A, B and C, assuming that all arithmetics is calculated in a k-bit unsigned integer type (with values 0 <= x < 2k) modulo 2k.

    Input

    The input consists of several instances. Each instance is described by a single line with four integers A, B, C, k separated by a single space. The integer k (1 <= k <= 32) is the number of bits of the control variable of the loop and A, B, C (0 <= A, B, C < 2k) are the parameters of the loop.

    The input is finished by a line containing four zeros.

    Output

    The output consists of several lines corresponding to the instances on the input. The i-th line contains either the number of executions of the statement in the i-th instance (a single integer number) or the word FOREVER if the loop does not terminate.

    Sample Input

    3 3 2 16
    3 7 2 16
    7 3 2 16
    3 4 2 16
    0 0 0 0
    

    Sample Output

    0
    2
    32766
    FOREVER

    Source

    题意:(a+bx)%(2^k)==c,求x最小值;
    思路:解扩展欧几里德;
    #include<iostream>
    #include<string>
    #include<cstring>
    #include<algorithm>
    #include<cstdio>
    using namespace std;
    #define ll long long
    #define esp 1e-13
    const int N=1e4+10,M=1e6+50000,inf=1e9+10,mod=1000000007;
    void extend_Euclid(ll a, ll b, ll &x, ll &y)
    {
        if(b == 0)
        {
            x = 1;
            y = 0;
            return;
        }
        extend_Euclid(b, a % b, x, y);
        ll tmp = x;
        x = y;
        y = tmp - (a / b) * y;
    }
    ll gcd(ll a,ll b)
    {
        if(b==0)
            return a;
        return gcd(b,a%b);
    }
    ll pow1(ll x)
    {
        ll sum=1;
        for(ll i=0;i<x;i++)
        sum*=2;
        return sum;
    }
    int main()
    {
        ll x,y,i,z,t;
        while(~scanf("%lld%lld%lld%lld",&x,&y,&i,&t))
        {
            if(x==0&&y==0&&i==0&&t==0)
            break;
            ll m=pow1(t);
            ll c=((y-x)%m+m)%m;
            ll j,k;
            if(c%gcd(m,i)==0)
            {
                extend_Euclid(i,m,j,k);
                ll ans=j*(c/gcd(m,i));
                m=m/gcd(m,i);
                printf("%lld
    ",(ans%m+m)%m);
            }
            else
            printf("FOREVER
    ");
        }
        return 0;
    }
  • 相关阅读:
    软件工程——第六章 软件测试【转】
    软件工程——第五章 程序编码【转】
    软件工程——第四章 面向过程的软件设计方法 【转】
    软件工程——第三章 软件需求分析 【转】
    软件工程——第二章 软件计划 【转】
    如何修改远程桌面的端口号
    关于导出Excel
    软件工程——第一章 软件和软件工程的基本概念【转】
    重构代码的7个阶段
    hibernate @JoinColumn
  • 原文地址:https://www.cnblogs.com/jhz033/p/5766058.html
Copyright © 2011-2022 走看看