Largest palindrome product

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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.

1.枚举

1. 利用两个for循环枚举两个三位数相乘
2. 判断相乘的乘积是否是回文整数(将数字倒置判断是否等于原数字
3. 动态刷新最大回文整数

#include <iostream>
using namespace std;

//自定义判断回文数字func函数
int func(int num){
    int raw = num, reverse = 0;
    while(num){
        //(1)将x值的最后一位放入reverse中，并且向前移动一位
        reverse = reverse * 10 + num % 10;
        //(2)去掉x值的最后一位
        num /= 10;
    }
    return raw == reverse;
}

int main(){
    int ans = 0;
    //1.利用两个for循环枚举两个三位数相乘
    for(int i = 0; i < 1000; i++){
        for(int j = i; j < 1000; j++){
            //2.判断相乘的乘积是否为回文数字
            if(func(i * j)){
                //3.动态刷新最大回文数字
                ans = max(ans, i * j);
            }
        }
    }
    cout << ans << endl;
    return 0;
}
//时间复杂度:O(n*n)

2.回文数判断

//回文数字的判断
int func(int num){
    int raw = num, reverse = 0;
    while(num){
        //(1)将num值的最后一位放入reverse中，并且向前移动一位
        reverse = reverse * 10 + num % 10;
        //(2)去掉num值的最后一位
        num /= 10;
    }
    return raw == reverse;
}