Author : Dipu Kumar Mohanto
CSE, Batch - 6
BRUR.
Problem Statement : D. Easy Problem
Source : codeforces
Category : Dynamic Programing
Algorithm : DP on subsequence
Verdict : Accepted
#include "bits/stdc++.h"
using namespace std;
#define FI freopen("in.txt", "r", stdin)
#define FO freopen("out.txt", "w", stdout)
#define FAST ios_base::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL)
#define FOR(i, n) for (int i = 1; i <= n; i++)
#define For(i, n) for (int i = 0; i < n; i++)
#define ROF(i, n) for (int i = n; i >= 1; i--)
#define Rof(i, n) for (int i = n-1; i >= 0; i--)
#define FORI(i, n) for (auto i : n)
#define ll long long
#define ull unsigned long long
#define vi vector <int>
#define vl vector <ll>
#define pii pair <int, int>
#define pll pair <ll, ll>
#define mk make_pair
#define ff first
#define ss second
#define eb emplace_back
#define em emplace
#define pb push_back
#define ppb pop_back
#define All(a) a.begin(), a.end()
#define memo(a, b) memset(a, b, sizeof a)
#define Sort(a) sort(All(a))
#define ED(a) Sort(a), a.erase(unique(All(a)), a.end())
#define rev(a) reverse(All(a))
#define sz(a) (int)a.size()
#define max3(a, b, c) max(a, max(b, c))
#define min3(a, b, c) min(a, min(b, c))
#define maxAll(a) *max_element(All(a))
#define minAll(a) *min_element(All(a))
#define allUpper(a) transform(All(a), a.begin(), :: toupper)
#define allLower(a) transform(All(a), a.begin(), :: tolower)
#define endl '\n'
#define nl puts("")
#define ub upper_bound
#define lb lower_bound
#define Exp exp(1.0)
#define PIE 2*acos(0.0)
#define Sin(a) sin(((a)*PIE)/180.0)
#define EPS 1e-9
// Important Functions
// mo compare function : friend bool operator < (mo p, mo q) { int pb = p.l / block; int qb = q.l / block; if (pb != qb) return p.l < q.l; return (p.r < q.r) ^ (p.l / block % 2); }
// factorial MOD inverse : ll inv[maxn]; inline ll factorialInverse() { inv[1] = 1; for (int i = 2; i < maxn; i++) inv[i] = (MOD � (MOD / i)) * inv[MOD % i) % MOD; }
/**
* uses of PBDS:
* 1) *X.find_by_order(k) : returns k'th element
* 2) X.order_of_key(k) : count total element less than k
* 3) All other operations same as set
**/
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"
using namespace __gnu_pbds;
template <typename T> using orderset = tree <T, null_type, less <T>, rb_tree_tag, tree_order_statistics_node_update>;
/**
* uses of rope data structure:
* Initialize : rope <data_type> Rope;
* Insert single element : Rope.push_back()
* Insert a block of elements : Rope.insert(position after insert, newRope)
* Erase a block of elements : Rope.erase(starting position of deletion, size of deletion)
* Other Operations : Same as std::vector
* Iterator : Rope.mutable_begin(), Rope.mutable_end(), Rope.mutable_rbegin(), Rope.mutable_rend()
* Caution : Never use -- Rope.begin() iterator
**/
#include "ext/rope"
using namespace __gnu_cxx;
// rope <int> Rope;
// int dr[] = {1, -1, 0, 0}; // 4 Direction
// int dc[] = {0, 0, 1, -1};
// int dr[] = {0, 0, 1, -1, 1, 1, -1, -1}; // 8 Direction
// int dc[] = {1, -1, 0, 0, 1, -1, 1, -1};
// int dr[] = {-1, 1, -2, -2, -1, 1, 2, 2}; // knight Moves
// int dc[] = {-2, -2, -1, 1, 2, 2, 1, -1};
#define trace1(x) cerr << #x << ": " << x << endl;
#define trace2(x, y) cerr << #x << ": " << x << " | " << #y << ": " << y << endl;
#define trace3(x, y, z) cerr << #x << ": " << x << " | " << #y << ": " << y << " | " << #z << ": " << z << endl;
#define trace4(a, b, c, d) cerr << #a << ": " << a << " | " << #b << ": " << b << " | " << #c << ": " << c << " | " << #d << ": " << d << endl;
#define trace5(a, b, c, d, e) cerr << #a << ": " << a << " | " << #b << ": " << b << " | " << #c << ": " << c << " | " << #d << ": " << d << " | " << #e << ": " << e << endl;
#define trace6(a, b, c, d, e, f) cerr << #a << ": " << a << " | " << #b << ": " << b << " | " << #c << ": " << c << " | " << #d << ": " << d << " | " << #e << ": " << e << " | " << #f << ": " << f << endl;
inline int setbit(int mask, int pos) { return mask |= (1 << pos); }
inline int resetbit(int mask, int pos) { return mask &= ~(1 << pos); }
inline int togglebit(int mask, int pos) { return mask ^= (1 << pos); }
inline bool checkbit(int mask, int pos) { return (bool)(mask & (1 << pos)); }
#define popcount(mask) __builtin_popcount(mask) // count set bit
#define popcountLL(mask) __builtin_popcountll(mask) // for long long
inline int read() { int a; scanf("%d", &a); return a; }
inline ll readLL() { ll a; scanf("%lld", &a); return a; }
inline double readDD() { double a; scanf("%lf", &a); return a; }
template <typename T> string toString(T num) { stringstream ss; ss << num; return ss.str(); }
int toInt(string s) { int num; istringstream iss(s); iss >> num; return num; }
ll toLLong(string s) { ll num; istringstream iss(s); iss >> num; return num; }
#define inf 1e17
#define mod 1000000007
static const int maxn = 1e5 + 5;
static const int logn = 18;
ll dp[maxn][5];
bool memoize[maxn][5];
string text, pat;
int lenText, lenPat;
inline ll subsequence(int i, int j)
{
if (j == lenPat) return 1;
if (i >= lenText) return 0;
ll &ret = dp[i][j];
bool &mem = memoize[i][j];
if (mem) return ret;
mem = 1;
ll sum = 0;
if (text[i] == pat[j])
{
sum += subsequence(i+1, j+1);
sum += subsequence(i+1, j);
}
else
{
sum += subsequence(i+1, j);
}
return ret = sum;
}
ll dp2[maxn][5];
bool memoize2[maxn][5];
ll cost[maxn];
inline ll minimumCost(int i, int j)
{
if (j == lenPat) return inf;
if (i >= lenText) return 0;
ll &ret = dp2[i][j];
bool &mem = memoize2[i][j];
if (mem) return ret;
mem = 1;
ll sum = inf;
if (text[i] != pat[j])
{
sum = minimumCost(i+1, j);
}
else
{
ll sum1 = cost[i] + minimumCost(i+1, j);
ll sum2 = minimumCost(i+1, j+1);
sum = min(sum1, sum2);
}
return ret = sum;
}
int main()
{
//FI;
cin >> lenText;
lenPat = 4;
pat = "hard";
cin >> text;
ll koyta = subsequence(0, 0);
if (koyta == 0)
{
cout << "0";
return 0;
}
for (int i = 0; i < lenText; i++) cin >> cost[i];
ll mini = minimumCost(0, 0);
cout << mini;
}
