Question

我坚持使用我对Euler项目问题4的解决方案，我有以下代码应该可以工作，并且它会迭代解决问题，因为我已经研究和发现（993 * 913）：

// Michael Clover
// Project Euler
// Problem 4

/* A palindromic number reads the same both ways. The largest palindrome made from the    product of two 2-digit numbers is 9009 = 91  99.

Find the largest palindrome made from the product of two 3-digit numbers. */

#include <iostream>
#include <string>
#include <sstream>
#include <cstdlib>

using namespace std;

bool achieved = false; // change to true when the palindrome is found
string string_conversion = "";
string first_half = ""; // first half of string
string second_half = ""; // second half of string
stringstream conversion; // use this to convert integers to strings

int check(string first_half, string second_half) {
    if (first_half.compare(second_half) == 0) {
        achieved = true;
        return 0;
    }
    else {
        return 0;
    }
    return 0;
}

int convert(int result) {
    char temp;
    conversion << result;
    conversion >> string_conversion;
    if (string_conversion.size() == 6) {
        temp = string_conversion.at(0);
        //cout << "temp = " << temp << endl;
        first_half+=(temp);
        temp = string_conversion.at(1);
        //cout << "temp = " << temp << endl;
        first_half+=(temp);
        temp = string_conversion.at(2);
        //cout << "temp = " << temp << endl;
        first_half+=(temp);
        temp = string_conversion.at(5);
        //cout << "temp = " << temp << endl;
        second_half+=(temp);
        temp = string_conversion.at(4);
        //cout << "temp = " << temp << endl;
        second_half+=(temp);
        temp = string_conversion.at(3);
        //cout << "temp = " << temp << endl;
        second_half+=(temp);
        //cout << first_half << second_half << endl;
        check(first_half, second_half);
    }
    //if (string_conversion.size() == 5) {
        //cout << "The size of the string is 5" << endl;
        //exit(1);
    //}
    string_conversion = "";
    cout << first_half << endl;
    cout << second_half << endl;
    first_half.clear();
    second_half.clear();
    conversion.clear();
    conversion.str("");
    //cout << "conversion: " << conversion << endl;
    return 0;
}

int iterate(int operator_one, int operator_two) { // takes two numbers and iterates     through them, each time it is iterated, the result is passed to the convert    function to convert to string
    int two = operator_two;
        for (int i = operator_one; i > 100; i--) {
            int result = i * two;
            cout << i << "x" << two << endl;
            convert(result);
        }
    return 0;
}

int main() { // Use the stringstream to convert the numerical values into strings     which you can then use to check if they are palindromes
    int operator_one = 999;
    int operator_two = 999;
    while (achieved == false) {
        for (int i = operator_two; i > 100; i--) {
            iterate(999, i);
        }
    }
    cout << "The largest palindrome made from the product of two 3-digit numbers is: "     << string_conversion << endl;
    return 0;
}

该程序向下遍历所有数字，通过999x999向下，然后将6位数字分成两个字符串，结果的后半部分从后向前排列。如控制台中所示，使用cout＆lt;＆lt;在运行时，程序尝试993 * 913，second_half字符串和first_half字符串都包含906.我认为程序应该做的是在迭代后执行检查（字符串first_half，字符串second_half）函数并确定两者都是字符串匹配（应根据各种来源返回0）然后应该在check（）中启动if语句并将boolean achie设置为true，结束主语句中的程序并在退出程序之前打印结果。但它不会这样做，这是我的问题。感谢您的帮助。

Answer 1

除了我在此代码中看到的其他一些问题之外，我认为您的终止问题是因为您只在 achieved中的外部循环完成后检查main() 。因此内循环（iterate()）将一直持续到operator_one低于100，然后外循环将持续到operator_two低于100，然后才能实际检查终止条件。

坚持我的项目欧拉＃4的解决方案

1 个答案: