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HDU 5047 推公式+别样输出

题意:给n个‘M‘形,问最多能把平面分成多少区域

解法:推公式 : f(n) = 4n(4n+1)/2 - 9n + 1 = (8n+1)(n-1)+2

前面部分有可能超long long,所以要转化一下,令a = 8n+1, b = n-1,将两个数都化为a1*10^8+b1的形式,则

(a1*10^8+b1)(a2*10^8+b2) =(a1a2*10^8 + a1b2 + a2b1)*10^8 + b1b2 + 2,由于a1,a2最多2为10^4左右,中间的数就都不会超过long long 了,先打印出前面,再打8位的后面即可。

代码:

#include <iostream>#include <cstdio>#include <cstring>#include <cstdlib>#include <cmath>#define lll __int64#define ll long longusing namespace std;int main(){    ll n;    int t,cs = 1;    ll e = 100000000LL;    scanf("%d",&t);    getchar();    while(t--)    {        scanf("%I64d",&n);        ll a = 8LL*n+1LL;        ll b = n-1LL;        ll a1 = a/e;        ll b1 = a%e;        ll a2 = b/e;        ll b2 = b%e;        ll ans1 = a1*a2*e + a1*b2 + a2*b1 + (b1*b2+2LL)/e;        ll ans2 = (b1*b2+2LL)%e;        int res = ans2;        printf("Case #%d: ",cs++);        if(ans1 != 0)        {            printf("%I64d",ans1);            printf("%08d\n",res);        }        else            printf("%I64d\n",ans2);    }    return 0;}
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HDU 5047 推公式+别样输出