Openjudge-特殊密码锁（贪心）

原题链接：

         http://cxsjsxmooc.openjudge.cn/2018t2springw1/001/

实现代码：

#include <iostream>
#include <cstring>

using namespace std;

void filp(string &s,int i);

int main()
{
	int count = 0;
	string start,switchs,end;
	cin >> start >> end;

	switchs = start;

	for(unsigned int i =1;i<switchs.length();++i)
	{
		if(switchs[i-1] != end[i-1])
		{
			++count;
			filp(switchs,i);
		}
	}
	if(switchs == end)
		cout << count;
	else
	{
		switchs = start;
		count = 1;
		filp(switchs,0);
		for(unsigned int i =1;i<switchs.length();++i)
		{
			if(switchs[i-1] != end[i-1])
			{
				++count;
				filp(switchs,i);
			}
		}
		if(switchs == end)
			cout << count;
		else
			cout << "impossible";
	}
}

void filp(string &s,int i)
{
    if(s[i] == '1') s[i] = '0';
    else s[i] = '1';
	if(i == 0)
	{
	    if(s[i+1] == '1') s[i+1] = '0';
	    else s[i+1] = '1';
	}
	else if(i == (int)s.length()-1)
	{
		if(s[i-1] == '1') s[i-1] = '0';
	    else s[i-1] = '1';
	}
	else
	{
		if(s[i+1] == '1') s[i+1] = '0';
	    else s[i+1] = '1';
	    if(s[i-1] == '1') s[i-1] = '0';
	    else s[i-1] = '1';
	}
}