/**
 *两个字符串，通过删除/添加/修改变为相同的字符串的最少操作
 *字符串距离就是：操作+1
 *字符串的相似度为（1/操作+1）
 * */
#include <iostream>
#include <chrono>
using namespace std;
using namespace std::chrono;

int get_distance(char* left,int l_begin,int l_end, //微软的例子
		char* right,int r_begin,int r_end)
{
	if(l_begin>=l_end)
	{
		if(r_begin>=r_end)
			return 0;
		else
			return r_end-r_begin;
	}
	if(r_begin>=r_end)
	{
		if(l_begin>=l_end)
			return 0;
		else
			return l_end-l_begin;
	}
	if(left[l_begin]==right[r_begin])
		return get_distance(left,l_begin+1,l_end,
				right,r_begin+1,r_end);
	else
	{
		int op1=get_distance(left,l_begin+1,l_end,
				right,r_begin+1,r_end);
		int op2=get_distance(left,l_begin,l_end,
				right,r_begin+1,r_end);
		int op3=get_distance(left,l_begin+1,l_end,
				right,r_begin,r_end);
		int sum=[&]()
		{
			int mid;
			if(op1>=op2)
				mid=op2;
			else
				mid=op1;
			if(mid>op3)
				mid=op3;
			return mid+1;
		}();
		return sum;
	}
}

int** new_matrix(int l,int r)
{
	int** ptr=new int*[l];
	for(int i=0;i<l;++i)
	{
		ptr[i]=new int[r];
		for(int j=0;j<r;++j)
		{
			ptr[i][j]=-1;
		}
	}
	return ptr;
}

void delete_matrix(int** ptr,int l)
{
	for(int i=0;i<l;++i)
		delete[] ptr[i];
	delete[] ptr;
}

int get_distance_state(char* left,int l_begin,int l_end, //带状态
		char* right,int r_begin,int r_end,int** state)
{

	if(state[l_begin][r_begin]!=-1)
		return state[l_begin][r_begin];

	if(l_begin>=l_end)
	{
		if(r_begin>=r_end)
		{
			state[l_begin][r_begin]=0;
			return 0;
		}
		else
		{
			int dis=r_end-r_begin;
			state[l_begin][r_begin]=dis;
			return dis;
		}
	}
	if(r_begin>=r_end)
	{
		if(l_begin>=l_end)
		{
			state[l_begin][r_begin]=0;
			return 0;
		}
		else
		{
			int dis= l_end-l_begin;
			state[l_begin][r_begin]=dis;
			return dis;
		}
	}
	if(left[l_begin]==right[r_begin])
	{
		int dis=get_distance(left,l_begin+1,l_end,
				right,r_begin+1,r_end);
		state[l_begin][r_begin]=dis;
		return dis;
	}
	else
	{
		int op1=get_distance(left,l_begin+1,l_end,
				right,r_begin+1,r_end);
		int op2=get_distance(left,l_begin,l_end,
				right,r_begin+1,r_end);
		int op3=get_distance(left,l_begin+1,l_end,
				right,r_begin,r_end);
		int sum=[&]()
		{
			int mid;
			if(op1>=op2)
				mid=op2;
			else
				mid=op1;
			if(mid>op3)
				mid=op3;
			return mid+1;
		}();
		state[l_begin][r_begin]=sum;
		return sum;
	}
}

int main(int argc,char* argv[])
{
	char left[]={"fdac"};
	char right[]={"ac"};
	
	int** state=new_matrix(sizeof(left)/sizeof(char),
			sizeof(right)/sizeof(char));

	system_clock::time_point t_b=system_clock::now();
	for(int i=0;i<10000000;++i)
	{
		int dis=get_distance(left,0,sizeof(left)/sizeof(char),
			right,0,sizeof(right)/sizeof(char));
		cout<<"normal: "<<dis<<endl;
	}
	milliseconds ms=duration_cast<milliseconds>(system_clock::now()-t_b);
	cout<<"normal: "<<ms.count()<<endl;
	t_b=system_clock::now();
	for(int i=0;i<10000000;++i) //这里因为已经存储了状态，所以实际上主要是第一次运行的时间
	{
		int dis=get_distance_state(left,0,sizeof(left)/sizeof(char),
			right,0,sizeof(right)/sizeof(char),state);
		cout<<"with state: "<<dis<<endl;
	}
	ms=duration_cast<milliseconds>(system_clock::now()-t_b);
	cout<<"with state: "<<ms.count()<<endl;
	//cout<<get_distance(left,0,sizeof(left)/sizeof(char),
	//		right,0,sizeof(right)/sizeof(char))<<endl;
	delete_matrix(state,sizeof(left)/sizeof(char));
}