在这个java代码中找到右循环移位的错误（Codility）

Question

Recently I was given a codility problem which says the following code has a bug .
So, the code problem is that we have a 30-bit unsigned integer from N[29]... N[0] and performing the right cyclic shift (>>) should give us a number like N[0]N[29]... N[1] .

Our goal is to find the number of right shifts which produce the maximum value achievable from a given number.

For Example:
for N = 9736 (00 0000 0000 0000 0010 0110 0000 1000)
9736 >> 1 = 4868 -> 00 0000 0000 0000 0001 0011 0000 0100
.
.
.
9736 >> 11 = 809500676 -> 11 0000 0100 0000 0000 0000 0000 0100
.
.
till 30 (as we have 30 bits integers)

from the example above on the 11th iteration, we receive the maximum number possible for 9736. Hence the answer = 11

Given Code:

 int shift(int N) {
        int largest = 0;
        int shift = 0;
        int temp = N;

        for (int i = 1; i < 30; ++i) {
            int index = (temp & 1);
            temp = ((temp >> 1) | (index << 29));
          
            if (temp > largest) {
                largest = temp;
                shift = i;
            }
        }

        return shift;
    }

N is in range [0... 1,073,741,823]

I tried but couldn't find the bug here or the test case where this fails.

Answer 1

It fails for 0b10000...000 ( 0x20000000 ), Because the largest value is for shift ==0

the simplest solution is to define largest as N instead of 0 .