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 = ;
const int turn[][] = {{, }, { -, }, {, }, {, -}};
//priority_queue<int, vector<int>, less<int>> que;
//next_permutation
ll mod = 3e7;
int pop = ;
char f[][];
int dp1[][];
int dp2[][];
string a;
int main()
{
        int n, m, k;
        cin >> n >> m >> k;
        int anser = ;
        char ch;
        for (int i = ; i <= n; i++)
        {
                scanf("%s", f[i] + );
        }
        if (k == )
        {
                for (int i = ; i <= n; i++)
                {
                        for (int j = ; j <= m; j++)
                        {
                                ch = f[i][j];
                                if (ch == '.')
                                {
                                        anser++;
                                }
                        }
                }
                cout << anser << endl;
                return ;
        }
        for (int i = ; i <= n; i++)
        {
                for (int j = ; j <= m; j++)
                {
                        ch = f[i][j];
                        if (ch == '*')
                        {
                                dp1[i][j] = dp2[i][j] = ;
                        }
                        else
                        {
                                dp1[i][j] = dp1[i - ][j] + ;
                                dp2[i][j] = dp2[i][j - ] + ;
                                if (dp1[i][j] >= k)
                                {
                                        anser++;
                                }
                                if (dp2[i][j] >= k)
                                {
                                        anser++;
                                }
                        }
                }
        }
        cout << anser << endl;
        return ;
}

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 = ;
const int turn[][] = {{, }, { -, }, {, }, {, -}};
//priority_queue<int, vector<int>, less<int>> que;
//next_permutation
ll mod = 3e7;
int pop = ;
vector<int> tree[];
int visit[];
int vis[];
int dp[][];
int ans[];
int gone[];
int num[];
int aim[];
string a;
int anser = ;
int flag = ;
void dfs(int x)
{
        gone[x] = ;
        int len = tree[x].size();
        for (int i = ; i < len; i++)
        {
                int to = tree[x][i];
                if (gone[to] == )
                {
                        cout << - << endl;
                        exit();
                }
                else if (gone[to] == )
                {
                        for (int j = ; j < ; j++)
                        {
                                int add = num[x] == j;
                                dp[x][j] = max(dp[x][j], dp[to][j] + add);
                        }
                }
                else
                {
                        dfs(to);
                        for (int j = ; j < ; j++)
                        {
                                int add = num[x] == j;
                                dp[x][j] = max(dp[x][j], dp[to][j] + add);
                        }
                }
        }
        gone[x] = ;
}
int main()
{
        int n, m;
        int from, to;
        cin >> n >> m;
        cin >> a;
        for (int i = ; i < a.size(); i++)
        {
                num[i + ] = a[i] - 'a';
                dp[i + ][num[i + ]] = ;
        }
        for (int i = ; i <= m; i++)
        {
                scanf("%d %d", &from, &to);
                tree[from].pb(to);
        }
        for (int i = ; i <= n; i++)
        {
                if (!gone[i])
                {
                        dfs(i);
                }
        }
        for (int i = ; i <= n; i++)
        {
                for (int j = ; j <= ; j++)
                {
                        ans[i] = max(ans[i], dp[i][j]);
                }
                anser = max(anser, ans[i]);
        }
        cout << anser << endl;
        return ;
}