python/TangDou/XiTi/1148.cpp

#include <bits/stdc++.h>

using namespace std;

//判断是不是质数
bool isPrime(int n) { //最快的方法
    if (n < 2) return false;
    if (n == 2 || n == 3) return true;
    if (n % 6 != 1 && n % 6 != 5) return false;
    for (int i = 5; i <= floor(sqrt(n)); i += 6)
        if (n % i == 0 || n % (i + 2) == 0)
            return false;
    return true;
}

int main() {
    int n;
    cin >> n;
    cout << n << "=";
    int a[100] = {0};
    int b[100] = {0};

    int k = 0;
    for (int i = 2; i <= n / 2; ++i) {
        if (isPrime(i)) {
            a[k] = i;
            k++;
        }
    }


    for (int i = 0; i < k;) {
        if (n % a[i] == 0) {
            n = n / a[i];
            b[i]++;
        } else {
            i++;
        }
    }


    //最后一个不是0的，就是停止位
    int lastIndex=0;
    for (int i = k-1; i >=0 ; i--) {
        if(b[i]>0) {
            lastIndex=i;
            break;
        }
    }

    //输出
    for (int i = 0; i <= lastIndex; i++) {
        if (b[i] > 1) {
            cout << a[i] << "^" << b[i];
            if (i < lastIndex) cout << "*";
        } else if (b[i] == 1) {
            cout << a[i];
            if (i < lastIndex) cout << "*";
        }
    }
    return 0;
}