项目欧拉＃8，似乎无法得到正确的答案

Question

我试图完成对项目欧拉出于某种原因，如果我使用（的int，long或long long）在我countAndMult功能我得到2091059712号8作为最不合适的数字。

我已阅读其他职位，这和我试图改变以下几点：

type   ----> output 
int   ----> 2091059712 
long   ----> 2091059712 
long long  ----> 2091059712 
unsigned long ----> 3780710640 

这里是我的代码：http://pastebin.com/KBsXxPjB

#include <iostream> 
#include <vector> 
using namespace std; 

void sliceString(string str, char arrChar[], int arrInt[], const int x){ 
    for(int i = 0; i<x; i++){ 
     arrChar[i] = {' '}; 
     arrInt[i] = {0}; 
    } 

    for(int i=0;i<x;i++){ 
     arrChar[i] = {str.at(i)}; 
    } 
} 

void charToInt(char arrChar[], int arrInt[], const int x){ 

    for(int i=0; i<x; i++){ 

     int doMath = arrChar[i]-48; 

     switch (doMath){ 
     case 0: 
      arrInt[i] = {doMath}; 
      break; 

     case 1: 
      arrInt[i] = {doMath}; 
      break; 
     case 2: 
      arrInt[i] = {doMath}; 
      break; 
     case 3: 
      arrInt[i] = {doMath}; 
      break; 
     case 4: 
      arrInt[i] = {doMath}; 
      break; 
     case 5: 
      arrInt[i] = {doMath}; 
      break; 
     case 6: 
      arrInt[i] = {doMath}; 
      break; 
     case 7: 
      arrInt[i] = {doMath}; 
      break; 
     case 8: 
      arrInt[i] = {doMath}; 
      break; 
     case 9: 
      arrInt[i] = {doMath}; 
      break; 
     } 
    } 
} 

unsigned long countAndMult(int arrInt[], const int x){ 

    unsigned long biggestSum = 0; 
    unsigned long tempSum = 0; 

    for(int i=0; i<x; i++){ 
     tempSum = arrInt[i]*arrInt[i+1]*arrInt[i+2]*arrInt[i+3]*arrInt[i+4]*arrInt[i+5]*arrInt[i+6]*arrInt[i+7]*arrInt[i+8]*arrInt[i+9]*arrInt[i+10]*arrInt[i+11]*arrInt[i+12]; 
     if(tempSum > biggestSum){ 
      biggestSum = tempSum; 
      cout << "arrInt[" << i << "] :: " << tempSum << endl; 
     } 
    } 
    return biggestSum; 
} 

int main(){ 
        //
    string number = "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450"; 
    string test = "7316717653133"; 

    const int SIZE = 1000; 
    char digits[SIZE]; 
    int actualDigits[SIZE]; 

    sliceString(number, digits, actualDigits, SIZE); 

    charToInt(digits, actualDigits, SIZE); 

    cout << countAndMult(actualDigits, SIZE) << endl; 

    return 0; 
} 

Answer 1

当您使用long long tempSum;，你这样做太晚了。数学已经完成了一个较小的类型（int，因为这是arrInt是），而高位早已不复存在。

你需要做转换前这将溢出的操作。例如：

tempSum = arrInt[i]*arrInt[i+1]*arrInt[i+2]*arrInt[i+3]*arrInt[i+4]*arrInt[i+5]* 
      (long long)(arrInt[i+6]*arrInt[i+7]*arrInt[i+8]*arrInt[i+9]*arrInt[i+10]*arrInt[i+11]*arrInt[i+12]);