//加法
public static int add(int a, int b)
{
int ans;
while(b!=0)
{
ans = a^b;
b = ((a&b)<<1);
a = ans;
}
return a;
}
//减法
public static int sub(int a, int b)
{
return add(a, -b);
}
//正数乘法
private static int posMultiply(int a,int b)
{
int ans = 0;
while(b>0)
{
if((b&0x1)==1)ans = add(ans, a);
a = (a<<1);
b = (b>>1);
}
return ans;
}
//乘法
public static int multiply(int a,int b)
{
if(a==0||b==0)return 0;
if(a>0 && b>0)
return posMultiply(a, b);
if(a<0)
{
if(b<0)
{
return posMultiply(-a, -b);
}
else
{
return -posMultiply(-a, b );
}
}
else
{
return -posMultiply(a, -b);
}
}
//正数除法
private static int posDiv(int x,int y)
{
int ans=0;
for(int i=31;i>=0;i--)
{
if((x>>i)>=y)
{
ans+=(1<<i);
x-=(y<<i);
}
}
return ans;
}
//除法
public static int div( int a, int b )
{
assert(b!=0);
if(a==0)return 0;
if(a>0)
{
if(b>0)
{
return posDiv(a,b);
}
else
{
return -posDiv( a,-b);
}
}
else
{
if(b>0)
{
return -posDiv(a, b);
}
else
{
return -posDiv(-a, -b);
}
}
}
//求负数
public static int negtive(int a)
{
return add(~a, 1);
}
//比较正数大小
private static boolean isbigerPos( int a, int b )
{
int c = 1;
b = (a^b);
if(b==0)return false;
while(b>0)
{
b>>=1;
c <<= 1;
}
return (c&a)==0;
}
//比较大小
public static boolean isbiger( int a, int b )
{
if(a<0)
{
if(b<0)
{
return isbigerPos( negtive(b), negtive(a) );
}
else
{
return false;
}
}
else
{
if(b<0)
{
return true;
}
else
{
return isbigerPos(a, b);
}
}
}
public static int divideby3(int x)
{
int sum = 0;
while(x > 3)
{
sum = add(x>>2 , sum);
x = add(x>>2 , x&3);
}
if(x == 3)
{
sum = add(sum , 1);
}
return sum;
}
public static void main(String[] args)
{
System.out.println(add(13,19));
System.out.println(sub(13,19));
System.out.println(multiply(13,19));
System.out.println(div(10,5));
System.out.println(negtive(13));
System.out.println(isbiger(10,5));
System.out.println(isbiger(10,11));
System.out.println(divideby3(15));
System.out.println(divideby3(14));
System.out.println(divideby3(13));
System.out.println(divideby3(12));
System.out.println(divideby3(11));
}
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