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  • HDU 4704 Sum (2013多校10,1009题)

    Sum

    Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
    Total Submission(s): 94    Accepted Submission(s): 41


    Problem Description
     
    Sample Input
    2
     
    Sample Output
    2
    Hint
    1. For N = 2, S(1) = S(2) = 1. 2. The input file consists of multiple test cases.
     
    Source
     
    Recommend
    zhuyuanchen520
     

    其实这题就是求2^(n-1) % MOD;

    可先对(n-1)%(MOD-1)

    这样就很容易求了

     1 /* ***********************************************
     2 Author        :kuangbin
     3 Created Time  :2013/8/22 12:00:50
     4 File Name     :F:2013ACM练习2013多校101009.cpp
     5 ************************************************ */
     6 
     7 #include <stdio.h>
     8 #include <string.h>
     9 #include <iostream>
    10 #include <algorithm>
    11 #include <vector>
    12 #include <queue>
    13 #include <set>
    14 #include <map>
    15 #include <string>
    16 #include <math.h>
    17 #include <stdlib.h>
    18 #include <time.h>
    19 using namespace std;
    20 
    21 const int MOD = 1e9+7;
    22 long long n;
    23 long long solve()
    24 {
    25     long long ret = 1;
    26     long long tmp = 2;
    27     while( n > 0)
    28     {
    29         if(n%2)
    30         {
    31             ret *= tmp;
    32             ret %= MOD;
    33         }
    34         tmp *= tmp;
    35         tmp %= MOD;
    36         n = n/2;
    37     }
    38     return ret;
    39 }
    40 char str[5000000];
    41 int main()
    42 {
    43     //freopen("in.txt","r",stdin);
    44     //freopen("out.txt","w",stdout);
    45     while(scanf("%s",str) == 1)
    46     {
    47         n = 0;
    48         int len = strlen(str);
    49         for(int i = 0;i < len;i++)
    50         {
    51             n = (n*10 + str[i] -'0')%(MOD-1);
    52         }
    53         n = (n-1+MOD-1)%(MOD-1);
    54         printf("%d
    ",(int)solve());
    55     }
    56     return 0;
    57 }
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  • 原文地址:https://www.cnblogs.com/kuangbin/p/3275593.html
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