Question

我正在尝试在项目euler上完成第8项，并且出于某种原因，如果我在countAndMult函数中使用（int，long或long long），我得到2091059712作为最大数字，这是不对的。

我已阅读其他帖子，我尝试更改为以下内容：

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

这是我的代码：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(){
                    //0123456789012
    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;时，您执行得太晚了。数学已经用较小的类型（int完成，因为arrInt是什么），而且高位已经很久了。

您需要在操作之前执行转换，否则会溢出。类似的东西：

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]);

项目欧拉＃8，似乎无法得到正确的答案

1 个答案: