子序列与子串问题总结

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

int DoubleEndLIS(vector<int> data)//当然也可以使用O(nlogn)的算法
{
	int length = data.size(),i,j,res = length;
	if(length == 0)return 0;
	vector<int> B(length,1),C(length,1);
	for(i = 0;i < length;++i)//从左向右
	{
		for(j = 0;j < i;++j)
		{
			if(data[j] < data[i] && B[j]+1 > B[i])B[i] = B[j]+1;
		}
	}
	for(i = length-1;i >= 0;--i)//从右向左
	{
		for(j = length-1;j > i;--j)
		{
			if(data[j] < data[i] && C[j]+1 > C[i])C[i] = C[j]+1;
		}
	}
	for(i = 0;i < length;++i)
	{
		if(length - B[i] - C[i] + 1 < res)res = length - B[i] - C[i] + 1;
	}
	return res;
}

int main()
{
	int n,i;
	while(cin >> n)
	{
		vector<int> data(n);
		for(i=0;i < n;++i)cin >> data[i];
		cout << DoubleEndLIS(data) << endl;
	}
}