Submission #246598

#	Time	Username	Problem	Language	Result	Execution time	Memory
246598		ritikpatel05	Walking (NOI12_walking)	C++17	25 / 25	10 ms	2432 KiB

walking

/*
	Author: Ritik Patel
*/
 
 
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& STL DEBUGGER &&&&&&&&&&&&&&&&&&&&&&&&&&&
 
// #define _GLIBCXX_DEBUG       // Iterator safety; out-of-bounds access for Containers, etc.
// #pragma GCC optimize "trapv" // abort() on (signed) integer overflow.
 
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& LIBRARIES &&&&&&&&&&&&&&&&&&&&&&&&&&&
 
#include <bits/stdc++.h>
using namespace std;
 
/*#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update
template<typename T, typename V = __gnu_pbds::null_type>
using ordered_set = __gnu_pbds::tree<T, V, less<T>, __gnu_pbds::rb_tree_tag, __gnu_pbds::tree_order_statistics_node_update>; 
*/
//find_by_order()->returns an iterator to the k-th largest element(0-based indexing)
//order_of_key()->Number of items that are strictly smaller than our item
 
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& DEFINES &&&&&&&&&&&&&&&&&&&&&&&&&&&
 
#define int long long int
// #define ll long long int
#define all(i) i.begin(), i.end()
#define sz(a) (int)a.size()
 
// #define ld long double
// const ld PI  = 3.141592;
const int dx4[4] = {0, 1, 0, -1};
const int dy4[4] = {-1, 0, 1, 0};
const int dx8[8] = {-1, -1, -1, 0, 1, 1, 1, 0};
const int dy8[8] = {-1, 0, 1, 1, 1, 0, -1, -1};
 
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& DEBUG &&&&&&&&&&&&&&&&&&&&&&&&&&&
 
#define XOX
vector<string> vec_splitter(string s) {
    for(char& c: s) c = c == ','?  ' ': c;
    stringstream ss; ss << s;
    vector<string> res;
    for(string z; ss >> z; res.push_back(z));
    return res;
}
 
void debug_out(vector<string> __attribute__ ((unused)) args, __attribute__ ((unused)) int idx) { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(vector<string> args, int idx, Head H, Tail... T) {
    if(idx > 0) cerr << ", ";
    stringstream ss; ss << H;
    cerr << args[idx] << " = " << ss.str();
    debug_out(args, idx + 1, T...);
}
 
#ifdef XOX
#define debug(...) debug_out(vec_splitter(#__VA_ARGS__), 0, __VA_ARGS__)
#else
#define debug(...) 42
#endif
 
 
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& CODE &&&&&&&&&&&&&&&&&&&&&&&&&&&
 
int L, N;
vector<pair<int,  pair<int, int>>> v(505);
vector<pair<double, int>> arrival;

int memo[505][505];

int dp(int id1, int id2){
    if(id1 >= N or id2 >= N){
        return 0;
    }
    auto &res = memo[id1][id2];
    if(res != -1){
        return res;
    }
    res = 0;
    if(v[id1].second.second == arrival[id2].second){
        res = max(res, 1 + dp(id1 + 1, id2 + 1));
    }
    res = max(res, dp(id1 + 1, id2));
    res = max(res, dp(id1, id2 + 1));
    return res;
}



void solve(){
    cin >> L >> N;
    v.resize(N); arrival.resize(N);
    for(int i = 0; i < N; ++i){
        cin >> v[i].first >> v[i].second.first;
        v[i].second.second = i;
    }
    
    
    for(int i = 0; i < N; ++i){
        double time = (double)L/(double)v[i].second.first + (double)v[i].first;
        arrival[i] = {time, v[i].second.second};
    }

    sort(all(v));
    sort(all(arrival));
    reverse(all(arrival));

    memset(memo, -1, sizeof(memo));
    cout << dp(0, 0) << '\n';   
}
 
 
 
int32_t main(){
    ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr); 
    int T = 1; 
    // cin >> T;
    for(int i = 1; i <= T; ++i){
        // brute();
        solve();
    }
    return 0;
}
 
/*
Sample inp
*/

• Subtask 1: 3 / 3
• Subtask 2: 3 / 3
• Subtask 3: 5 / 5
• Subtask 4: 7 / 7
• Subtask 5: 7 / 7