Codeforces 919 行+列前缀和 树上记忆化搜索(树形DP)

A

B

C

#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-8;
typedef pair<int, int> pairint;
typedef long long ll;
typedef unsigned long long ull;
//const int maxn = 3e5 + 10;
const int  maxm = 300;
const int turn[4][2] = {{1, 0}, { -1, 0}, {0, 1}, {0, -1}};
//priority_queue<int, vector<int>, less<int>> que;
//next_permutation
ll mod = 3e7;
int pop = 0;
char f[2005][2005];
int dp1[2005][2005];
int dp2[2005][2005];
string a;
int main()
{
        int n, m, k;
        cin >> n >> m >> k;
        int anser = 0;
        char ch;
        for (int i = 1; i <= n; i++)
        {
                scanf("%s", f[i] + 1);
        }
        if (k == 1)
        {
                for (int i = 1; i <= n; i++)
                {
                        for (int j = 1; j <= m; j++)
                        {
                                ch = f[i][j];
                                if (ch == '.')
                                {
                                        anser++;
                                }
                        }
                }
                cout << anser << endl;
                return 0;
        }
        for (int i = 1; i <= n; i++)
        {
                for (int j = 1; j <= m; j++)
                {
                        ch = f[i][j];
                        if (ch == '*')
                        {
                                dp1[i][j] = dp2[i][j] = 0;
                        }
                        else
                        {
                                dp1[i][j] = dp1[i - 1][j] + 1;
                                dp2[i][j] = dp2[i][j - 1] + 1;
                                if (dp1[i][j] >= k)
                                {
                                        anser++;
                                }
                                if (dp2[i][j] >= k)
                                {
                                        anser++;
                                }
                        }
                }
        }
        cout << anser << endl;
        return 0;
}

D

#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-8;
typedef pair<int, int> pairint;
typedef long long ll;
typedef unsigned long long ull;
//const int maxn = 3e5 + 10;
const int  maxm = 300;
const int turn[4][2] = {{1, 0}, { -1, 0}, {0, 1}, {0, -1}};
//priority_queue<int, vector<int>, less<int>> que;
//next_permutation
ll mod = 3e7;
int pop = 0;
vector<int> tree[300005];
int visit[300005];
int vis[300005];
int dp[300005][30];
int ans[300005];
int gone[300005];
int num[300005];
int aim[30];
string a;
int anser = 0;
int flag = 0;
void dfs(int x)
{
        gone[x] = 1;
        int len = tree[x].size();
        for (int i = 0; i < len; i++)
        {
                int to = tree[x][i];
                if (gone[to] == 1)
                {
                        cout << -1 << endl;
                        exit(0);
                }
                else if (gone[to] == 2)
                {
                        for (int j = 0; j < 26; j++)
                        {
                                int add = num[x] == j;
                                dp[x][j] = max(dp[x][j], dp[to][j] + add);
                        }
                }
                else
                {
                        dfs(to);
                        for (int j = 0; j < 26; j++)
                        {
                                int add = num[x] == j;
                                dp[x][j] = max(dp[x][j], dp[to][j] + add);
                        }
                }
        }
        gone[x] = 2;
}
int main()
{
        int n, m;
        int from, to;
        cin >> n >> m;
        cin >> a;
        for (int i = 0; i < a.size(); i++)
        {
                num[i + 1] = a[i] - 'a';
                dp[i + 1][num[i + 1]] = 1;
        }
        for (int i = 1; i <= m; i++)
        {
                scanf("%d %d", &from, &to);
                tree[from].pb(to);
        }
        for (int i = 1; i <= n; i++)
        {
                if (!gone[i])
                {
                        dfs(i);
                }
        }
        for (int i = 1; i <= n; i++)
        {
                for (int j = 0; j <= 25; j++)
                {
                        ans[i] = max(ans[i], dp[i][j]);
                }
                anser = max(anser, ans[i]);
        }
        cout << anser << endl;
        return 0;
}