Given a string containing the only symbols '+' or '-', how do we find the minimum number of changes to transform it to a chain. A chain of length N is the sequence of alternative + and - symbols.

min_changes.cpp

#include <iostream>
#include <string>
using namespace std;

int main()
{
	cin.sync_with_stdio(false);
	int t;
	cin >> t;
	while(t--)
	{
		string input;
		cin >> input;
		int i, result = 0, result1 = 0;
		char p1 = '+', p2 = '-';
		for( i = 0; i < input.size(); i++ )
		{
			if( input[i] != p1 )
				result++;
			if( input[i] != p2 )
				result1++;
			p1 = (p1 == '+')? '-':'+';
			p2 = (p2 == '+')? '-':'+';
		}
		cout << min(result,result1) << endl;
	}
	return 0;
}