英文:
Why don't I get positive values when trying to divide two integers (without using multiplication, div, mod, log)?
问题
在 int divide() 方法中，Math.abs() 对上下边界值返回负值。即使我将其与 *-1 相乘，负数仍然不会转换为正值（div 显示为负数），但当我在 main() 方法中尝试使用 Math.abs() 时，相同的方法有效。
public class Mass {
public static int divide(int dividend, int divisor) {
int ans = 0;
long val = Math.abs(divisor);
long div = Math.abs(dividend);
System.out.println(div);
for (int i = 1; i <= div; i++) {
val--;
if (val == 0) {
ans++;
val = Math.abs(divisor);
}
}
if ((dividend < 0 && divisor > 0) || (dividend > 0 && divisor < 0)) {
ans = ans * (-1);
}
return ans;
}
public static void main(String[] args) {
int a = divide(-2147483648, -2);
System.out.println(a);
}
}
为什么我在处理负数值时遇到问题？
英文:
In the int divide() method, Math.abs() is returning negative values for upper and lower boundary values. Even if I multiply it with *-1 the negative is not converting into positive value (div is showing a negative value), but the same methods works when I tried Math.abs() in main() method.
public class Mass {
public static int divide(int dividend, int divisor) {
int ans =0;
long val = Math.abs(divisor);
long div = Math.abs(dividend);
System.out.println(div);
for(int i =1;i<=div;i++){
val--;
if(val ==0){
ans++;
val = Math.abs(divisor);
}
}
if((dividend<0 && divisor >0 ) || (dividend >0 && divisor<0) ){
ans = ans *(-1);
}
return ans;
}
public static void main(String[] args) {
int a= divide(-2147483648, -2);
System.out.println(a);
}
}
Why do I have trouble with negative values?
答案1
得分: 2
在Java中，int有32位，所以最小值是-2147483648，最大值是2147483647。这意味着当你计算abs(min)时会发生溢出。
我认为实际上解决这个问题的最简单方法是使用负数，类似这样：
public int divide(int dividend, int divisor) {
if (divisor == 0 || dividend == Integer.MIN_VALUE && divisor == -1) throw new IllegalArgumentException();
if (dividend == 0) return 0;
if (divisor == 1) return dividend; // dividend = MIN_VALUE时需要这个
boolean negative = false;
if (dividend > 0) dividend = -dividend; else negative = true;
if (divisor > 0) divisor = -divisor; else negative = !negative;
int result = 0;
for (; dividend <= divisor; result++) dividend -= divisor;
return negative ? -result : result;
}
英文:
ints in Java have 32 bits, so the min is -2147483648 and the max is 2147483647. This means you get overflow when you do abs(min).
I think actually the easiest way to fix this is just working with negative numbers, something like this:
public int divide(int dividend, int divisor) {
if (divisor == 0 || dividend == Integer.MIN_VALUE && divisor == -1) throw new IllegalArgumentException();
if (dividend == 0) return 0;
if (divisor == 1) return dividend; // required for dividend = MIN_VALUE
boolean negative = false;
if (dividend > 0) dividend = -dividend; else negative = true;
if (divisor > 0) divisor = -divisor; else negative = !negative;
int result = 0;
for (; dividend <= divisor; result++) dividend -= divisor;
return negative ? -result : result;
}
答案2
得分: 1
//仅适用于整数
public class MathSkills {
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(dividend(100, 4));
}
public static int dividend(int a, int b) {
int ans=0;
for(;a>=b;ans++) {
a=a-b;
}
return ans;
}
}
英文:
//works for integers only
public class MathSkills {
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(dividend(100,4));
}
public static int dividend(int a, int b) {
int ans=0;
for(;a>=b;ans++) {
a=a-b;
}
return ans;
}
}
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