hdu5666 Segment (俄罗斯乘法)

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题目链接：点这里！！！！

题意：求(q-1)*(q-2)%p,(1<=q<=1e18,q is primer, 1<=p<=1e18)

题解：直接俄罗斯乘法就可以了。

俄罗斯乘法：点这里！！

代码：

#include<cstdio>#include<cstring>#include<iostream>#include<sstream>#include<algorithm>#include<vector>#include<bitset>#include<set>#include<queue>#include<stack>#include<map>#include<cstdlib>#include<cmath>#define PI 2*asin(1.0)#define LL long long#define pb push_back#define pa pair<int,int>#define clr(a,b) memset(a,b,sizeof(a))#define lson lr<<1,l,mid#define rson lr<<1|1,mid+1,r#define bug(x) printf("%d++++++++++++++++++++%d\n",x,x)#define key_value ch[ch[root][1]][0]C:\Program Files\Git\binconst int  MOD = 1000000007;const int N = 500+15;const int maxn = 60000+1000;const int letter = 130;const int INF = 1e17;const double pi=acos(-1.0);const double eps=1e-8;using namespace std;inline int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}    return x*f;}LL p,q,x,y;LL cc(LL a,LL b){    LL ans=0,pc=a;    while(b){        if(b&1){            ans=(ans+pc)%p;            b--;        }        else {            pc=(pc*2)%p;            b=b/2;        }    }    return ans;}int main(){    int T;    scanf("%d",&T);    while(T--){        scanf("%I64d%I64d",&q,&p);        if(q<=2) {puts("0");continue;}        LL x,y;        if((q-2)&1) x=q-2,y=(q-1)/2ll;        else x=(q-2)/2ll,y=q-1;        LL ans=cc(x,y);        printf("%I64d\n",ans);    }    return 0;}

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