解析

#include<cstdio>
#include<cmath>
#include<vector>
using namespace std;
vector<bool> prime;
vector<int> PNum;
struct factor {
	int x, cnt;
}fac[10];
void makePrime(int N){
	prime.resize(N+1, false);
	for (int i = 2; i <= N; i++) {
		if (prime[i] == false
 
) {
			PNum.push_back(i);
			for (int j = i + i; j <= N; j += i)
				prime[j] = true;
		}
	}
}
int main()
{
	int N;
	scanf("%d", &N);
	if (N == 1)
		printf("1=1");
	else {
		int SQRT = (int)sqrt(N*1.0), num = N, go = 0;
		makePrime(SQRT);
		for (int i = 0; i < PNum.size() && PNum[i] <=
 
 SQRT; i++) {
			if (num%PNum[i] == 0) {
				fac[go].x = PNum[i];
				while (num%PNum[i] == 0) {
					fac[go].cnt++;
					num /= PNum[i];
				}
				go++;
			}
		}
		if (num != 1) {
			fac[go].x = num;
			fac[go++].cnt = 1;
		}
		printf("%d=", N);
		for (int i = 0; i < go; i++) {
			if (fac[i].cnt == 1
 
)
				printf("%d%c", fac[i].x, i == go - 1 ? '\n' : '*');
			else
				printf("%d^%d%c", fac[i].x, fac[i].cnt, i == go - 1 ? '\n' : '*');
		}
	}
}
/*
97532468
*/