Why I am getting -2147483648 and -1's multiplication, negative i.e. -2147483648, instead it should be +2147483648 [duplicate]

问题

This is the code snippet I had written for this question in Leetcode.

 public static int quotient(int dividend,int divisor){
        int n=Math.abs(divisor),count=0,ans=Integer.MAX_VALUE-1;
        if(Math.abs(dividend)==1 && Math.abs(divisor)==1){
            return dividend*divisor;
        }
        else if(Math.abs(divisor)==1){
            if(dividend<0 && divisor<0)
                return Math.abs(dividend);
            return dividend*divisor;
        }
        else if(dividend==0){
            return 0;
        }
        else {
            while (true) {
                if (n > Math.abs(dividend)) {
                    ans = count;
                    break;
                } else if (n == Math.abs(dividend)) {
                    ans = count + 1;
                    break;
                } else {
                    n += Math.abs(divisor);
                    count++;
                }
            }
        }
        if((dividend<0 && divisor>0) || (dividend>0 && divisor<0))
              ans*=-1;
        return ans;
    }
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int dividend=sc.nextInt();
        int divisor = sc.nextInt();
        int ans=quotient(dividend,divisor);
        System.out.println(ans);

}

but this code is failing for this test case and I am getting its output as -2147483648and the expected output is 2147483648. I tried using Math.abs(_) but it is also not working.

Inputs:

-2147483648 -1

Why is this happening? Please explain.

回答1:

I think this is an Integer overflow. As shown here, the maximum value of Long Integer is 2147483647, and there is no such int value as 2147483648, so it goes to -2147483648 as the next integer when adding 1. You can try the long type for solving this problem, its maximum is 9223372036854775807 in Java (that's a lot).

来源：https://stackoverflow.com/questions/64832530/why-i-am-getting-2147483648-and-1s-multiplication-negative-i-e-2147483648

标签

java

integer