write a go solution for Description:
A binary string is a string consisting only of the characters 0 and 1. You are given a binary string s_1s_2ldotss_n. It is necessary to make this string non-decreasing in the least number of operations. In other words, each character should be not less than the previous. In one operation, you can do the following:

- Select an arbitrary index 1<=i<=n in the string;
- For all j>=qi, change the value in the j-th position to the opposite, that is, if s_j=1, then make s_j=0, and vice versa.

What is the minimum number of operations needed to make the string non-decreasing?

Input Format:
Each test consists of multiple test cases. The first line contains an integer t (1<=t<=10^4) — the number of test cases. The description of test cases follows.

The first line of each test cases a single integer n (1<=n<=10^5) — the length of the string.

The second line of each test case contains a binary string s of length n.

It is guaranteed that the sum of n over all test cases does not exceed 2*10^5.

Output Format:
For each test case, output a single integer — the minimum number of operations that are needed to make the string non-decreasing.

Note:
In the first test case, the string is already non-decreasing.

In the second test case, you can select i=1 and then s=mathtt01.

In the third test case, you can select i=1 and get s=mathtt010, and then select i=2. As a result, we get s=mathtt001, that is, a non-decreasing string.

In the sixth test case, you can select i=5 at the first iteration and get s=mathtt100001. Then choose i=2, then s=mathtt111110. Then we select i=1, getting the non-decreasing string s=mathtt000001.. Output only the code with no comments, explanation, or additional text.