VJ 1033 整数分解（版本2）

#include <iostream>
#include <cstdio>
#include <cstring>
#define REP(i, s, n) for(int i = s; i <= n; i ++)
#define REP_(i, s, n) for(int i = n; i >= s; i --)
#define MAX_N 1000 + 10

using namespace std;

int a[MAX_N],la=1;

void mul (int e){
    int s = 0, t = 0;
    REP(i, 0, la - 1){
        t = a[i] * e; a[i] = (t + s) % 10;
        s = (t + s) / 10;
    }
    while(s > 0){
        a[la ++] = s % 10;
        s /= 10;
    }
}

int main (){
    int n;
    scanf("%d",&n);
    memset (a, 0, sizeof (a));
    a[0] = 1;
    if(n%3==0){ REP(i, 1, n / 3) mul(3); }
    else if(n % 3 == 1){ 
        REP(i, 1, (n / 3 - 1)) mul(3);    
        mul(4);
    }
    else{
        REP(i, 1, n / 3) mul(3);
        mul(2);
    }
    if (n > 2)
        REP_(i, 0, la - 1) printf("%d",a[i]);
    else printf("%d",n);
    return 0;
}