Codeforces 934 最长不递减子序列多项式系数推导

给你一个长度为N的01串你可以翻转一次任意【L，R】的区间

问你最长的不递减序列为多少长

处理出1的前缀和和2的后缀和

然后N^2 DP 处理出【L,R】区间的最长不递增序列

#include <bits/stdc++.h>

#define PI acos(-1.0)

#define mem(a,b) memset((a),b,sizeof(a))

#define TS printf("!!!\n")

#define pb push_back

#define inf 1e9

//std::ios::sync_with_stdio(false);

using namespace std;

//priority_queue<int,vector<int>,greater<int>> que; get min

const double eps = 1.0e-10;

const double EPS = 1.0e-4;

typedef pair<int, int> pairint;

typedef long long ll;

typedef unsigned long long ull;

const int turn[][] = {{, }, { -, }, {, }, {, -}};

//priority_queue<int, vector<int>, less<int>> que;

//next_permutation

const int MAXN = ;

int a[];

int pre[];

int suf[];

int dp[][][];

int ans = ;

int main()

{

        ios::sync_with_stdio(false);

        cin.tie();

        int n;

        cin >> n;

        for (int i = ; i <= n; i++)

        {

                cin >> a[i];

        }

        for (int i = ; i <= n; i++)

        {

                pre[i] = pre[i - ] + (a[i] == );

        }

        for (int i = n; i >= ; i--)

        {

                suf[i] = suf[i + ] + (a[i] == );

        }

        for (int i = ; i <= n; i++)

        {

                ans = max(pre[i] + suf[i], ans);

        }

        //cout<<ans<<endl;

        for (int i = ; i <= n; i++)

        {

                for (int j = i; j <= n; j++)

                {

                        dp[i][j][] = dp[i][j - ][] + (a[j] == );

                        dp[i][j][] = max(dp[i][j - ][], dp[i][j - ][]) + (a[j] == );

                        ans = max(ans, max(dp[i][j][], dp[i][j][]) + pre[i - ] + suf[j + ]);

                }

        }

        cout << ans << endl;

}

找规律

考虑构造q(x).先让常数项小于k,也就是让相乘后的常数项+p小于k.

q(x)的常数项就是p / (-k).这样会产生一次项，那么继续消一次项.直到最后的p = 0.

#include <bits/stdc++.h>

#define PI acos(-1.0)

#define mem(a,b) memset((a),b,sizeof(a))

#define TS printf("!!!\n")

#define pb push_back

#define inf 1e9

//std::ios::sync_with_stdio(false);

using namespace std;

//priority_queue<int,vector<int>,greater<int>> que; get min

const double eps = 1.0e-10;

const double EPS = 1.0e-4;

typedef pair<int, int> pairint;

typedef long long ll;

typedef unsigned long long ull;

//const int maxn = 3e5 + 10;

const int turn[][] = {{, }, { -, }, {, }, {, -}};

//priority_queue<int, vector<int>, less<int>> que;

//next_permutation

ll Mod = ;

int cnt;

int ans[];

int main()

{

        ll p;

        ll k;

        cin >> p >> k;

        ll flag = ;

        while (p != )

        {

                ans[++cnt] = p % k;

                p = p / k * (-);

                if (flag)

                {

                        p += flag;

                        flag = ;

                }

                if (p < )

                {

                        flag += (k - p) / k;

                        p += flag * k;;

                }

        }

        cout << cnt << endl;

        for (int i = ; i <= cnt; i++)

        {

                cout << ans[i] << " ";

        }

        cout << endl;

        return ;

}

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Codeforces 934 最长不递减子序列多项式系数推导

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巴特西

Codeforces 934 最长不递减子序列 多项式系数推导

最新文章

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Codeforces 934 最长不递减子序列多项式系数推导