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c++ - C++ 中的 Project Euler 任务 #8,代码由于微妙的原因返回错误答案

转载 作者:行者123 更新时间:2023-11-30 01:17:23 25 4
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我正在解决 Project Euler 问题,但我很早就走到了死胡同 - 我几乎可以肯定我的代码是正确的,但我的答案没有被接受为正确的。

The four adjacent digits in the 1000-digit number that have the greatest product are 9 × 9 × 8 × 9 = 5832.

73167176531330624919225119674426574742355349194934 96983520312774506326239578318016984801869478851843 85861560789112949495459501737958331952853208805511 12540698747158523863050715693290963295227443043557 66896648950445244523161731856403098711121722383113 62229893423380308135336276614282806444486645238749 30358907296290491560440772390713810515859307960866 70172427121883998797908792274921901699720888093776 65727333001053367881220235421809751254540594752243 52584907711670556013604839586446706324415722155397 53697817977846174064955149290862569321978468622482 83972241375657056057490261407972968652414535100474 82166370484403199890008895243450658541227588666881 16427171479924442928230863465674813919123162824586 17866458359124566529476545682848912883142607690042 24219022671055626321111109370544217506941658960408 07198403850962455444362981230987879927244284909188 84580156166097919133875499200524063689912560717606 05886116467109405077541002256983155200055935729725 71636269561882670428252483600823257530420752963450

Find the thirteen adjacent digits in the 1000-digit number that have the greatest product. What is the value of this product?

我的方法很简单——这是我第一次在没有任何优化的情况下解决这个问题,只是想看看我是否能解决它:

#include <string>
#include <iostream>
#include <stdlib.h> // atol ASCII to Integer function


int main(){

std::string digits = "73167176531330624919225119674426574742355349194934";
digits += "96983520312774506326239578318016984801869478851843";
digits += "85861560789112949495459501737958331952853208805511";
digits += "12540698747158523863050715693290963295227443043557";
digits += "66896648950445244523161731856403098711121722383113";
digits += "62229893423380308135336276614282806444486645238749";
digits += "30358907296290491560440772390713810515859307960866";
digits += "70172427121883998797908792274921901699720888093776";
digits += "65727333001053367881220235421809751254540594752243";
digits += "52584907711670556013604839586446706324415722155397";
digits += "53697817977846174064955149290862569321978468622482";
digits += "83972241375657056057490261407972968652414535100474";
digits += "82166370484403199890008895243450658541227588666881";
digits += "16427171479924442928230863465674813919123162824586";
digits += "17866458359124566529476545682848912883142607690042";
digits += "24219022671055626321111109370544217506941658960408";
digits += "07198403850962455444362981230987879927244284909188";
digits += "84580156166097919133875499200524063689912560717606";
digits += "05886116467109405077541002256983155200055935729725";
digits += "71636269561882670428252483600823257530420752963450";

long product = 1;
long temp = 1;

for(int i = 12; i < digits.length(); i++){

for(int j = 0; j<13; j++){

temp = temp*atoi(digits.substr(i-j,1).c_str());
}

if(temp > product){
product = temp;
std::cout << "index: " << (i-12) << " Product: " << product << "\n";
}

temp = 1;
}

return 0;
}

这将返回以下答案:

index: 0 Product: 5000940
index: 16 Product: 9797760
index: 19 Product: 13063680
index: 21 Product: 25401600
index: 22 Product: 50803200
index: 23 Product: 71124480
index: 24 Product: 284497920
index: 25 Product: 568995840
index: 40 Product: 1020366720
index: 41 Product: 1632586752
index: 43 Product: 2040733440
index: 503 Product: 2091059712

因此,当然,我将最后一个数字提交给 P.E.网站,但被拒绝。

我已经做了非常明显的合理性检查(索引 503 处的 13 位数字实际上产生了 2091059712 吗?)是的,它们确实产生了,所以我没有在索引错误的地方做一些微妙的事情,只乘以 12 个数字(或 14)而不是正确的 13。

所以...什么可能使我的代码返回错误的数字?我是否在没有注意到的情况下不小心乘以了一个额外的零?我已经看了一个小时了,是时候让其他人关注我的代码了。

最佳答案

似乎 913 不适合您平台上的 long

您可以将 long 替换为 long long int 或其他更宽的整数。

live example给出以下输出

index: 0 Product: 5000940
index: 16 Product: 9797760
index: 19 Product: 13063680
index: 21 Product: 25401600
index: 22 Product: 50803200
index: 23 Product: 71124480
index: 24 Product: 284497920
index: 25 Product: 568995840
index: 40 Product: 1020366720
index: 41 Product: 1632586752
index: 43 Product: 2040733440
index: 88 Product: 2972712960
index: 195 Product: 6270566400
index: 196 Product: 14108774400
index: 197 Product: 23514624000

不犯这样的错误正是project euler要教给你的。

关于c++ - C++ 中的 Project Euler 任务 #8,代码由于微妙的原因返回错误答案,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/24529560/

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