二分查找、三分查找求极点、二分求等比数列【模板】

二分查找：

int a[110],N;int BinarySearch(int *a,int x){    int Left = a[1];    int Right = a[N];    while(Left <= Right)    {        int mid = (Left+Right)>>1;        if(a[mid] == x)            return mid;        else if(a[mid] > x)            Right = mid - 1;        else            Left = mid + 1;    }    return -1;}

三分查找求极点：

double left,right,mid,midmid;  left = 0;  right = PI/2;  while(right-left >= 1e-7)  {      mid = (left+right)/2;      midmid = (mid+right)/2;      if(calc(mid) > calc(midmid))          right = midmid;      else          left = mid;  }  

二分求等比数列

LL Power(LL p,LL n)  {      LL ret = 1;      while(n > 0)      {          if(n&1)              ret = ret * p % 9901;          p = p * p % 9901;          n >>= 1;      }      return ret;  }  LL Sum(LL p,LL n)  //递归二分求(1 + p^1 + p^2 + … + p^n)%mod{      if(n == 0)          return 1;      if(n&1)          return (Sum(p,n/2)*(1+Power(p,n/2+1)))%9901;      else          return (Sum(p,n/2-1)*(1+Power(p,n/2+1)) + Power(p,n/2))%9901;  }