Submission #1023184

#	Time	Username	Problem	Language	Result	Execution time	Memory
1023184		Wansur	Aliens (IOI16_aliens)	C++17	25 / 100	2060 ms	48760 KiB

aliens

#include <bits/stdc++.h>
#define ent '\n'
#define line pair<ll, ll>
#define k first
#define b second

typedef long long ll;
using namespace std;
const int maxn = 1e6+12;

vector<int> g[maxn];
bool was[maxn];
ll dp[maxn];
ll ndp[maxn];
int L[maxn];
int R[maxn];

bool check(line nw, line last, line prl){
    if((nw.b - prl.b) * (prl.k - last.k) <= (last.b - prl.b) * (prl.k - nw.k))return 1;
    return 0;
}

int ptr = 0;
vector<line> l;
void add(line x){
    while(l.size() && l.back().k == x.k && l.back().b > x.b){
        l.pop_back();
    }
    if(l.size() && l.back().k == x.k && l.back().b <= x.b){
        return;
    }
    while(l.size()>1 && check(x, l.back(), l[l.size()-2])){
        l.pop_back();
    }
    l.push_back(x);
}
ll get(ll x){
    if(!l.size()){
        return 1e12+1;
    }
    if(ptr >= l.size()){
        ptr = l.size()-1;
    }
    while(ptr + 1 < l.size() && l[ptr].k * x + l[ptr].b > l[ptr+1].k * x + l[ptr+1].b){
        ptr++;
    }
    return l[ptr].k * x + l[ptr].b;
}

long long take_photos(int n, int m, int k, vector<int> r, vector<int> c){
    for(int i=1;i<=m;i++){
        L[i] = 1e9;
    }
    m = 0;
    for(int i=0;i<n;i++){
        if(r[i] < c[i]){
            swap(r[i], c[i]);
        }
        r[i]++, c[i]++;
        L[r[i]] = min(L[r[i]], c[i]);
        R[c[i]] = max(R[c[i]], r[i]);
        for(int x=-1;x<=1;x++){
            was[r[i]+x] = was[c[i]+x] = 1;
        }
        m = max(m, r[i]);
    }
    was[1] = 1;
    vector<int> t;
    for(int i=1;i<=m;i++){
        dp[i] = ndp[i] = 1e12+1;
        R[i] = max(R[i], R[i-1]);
        if(!was[i]) continue;
        t.push_back(i);
        g[max(R[i], i)].push_back(i);
    }
    for(int _=1;_<=k;_++){
        add({0, 0});
        for(int &i:t){
            ndp[i] = get(i) + i * 1ll * i;
            for(int &j:g[i]){
                ll b = j * 1ll * j + dp[R[j]];
                if(R[j] > j) b -= (R[j] - j) * 1ll * (R[j] - j);
                add(line(-2 * j, b));
            }
        }
        for(int i=0;i<=m;i++){
            dp[i] = ndp[i];
        }
        ptr = 0;
        l.clear();
    }
    return dp[m];
}

Compilation message (stderr)

aliens.cpp: In function 'll get(ll)':
aliens.cpp:41:12: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   41 |     if(ptr >= l.size()){
      |        ~~~~^~~~~~~~~~~
aliens.cpp:44:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   44 |     while(ptr + 1 < l.size() && l[ptr].k * x + l[ptr].b > l[ptr+1].k * x + l[ptr+1].b){
      |           ~~~~~~~~^~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 12 / 12
• Subtask 3: 9 / 9
• Subtask 4: 0 / 16
• Subtask 5: 0 / 19
• Subtask 6: 0 / 40