Submission #426405

#	Time	Username	Problem	Language	Result	Execution time	Memory
426405		ngrace	Aliens (IOI16_aliens)	C++14	25 / 100	142 ms	2292 KiB

aliens

#include "aliens.h"
#include <vector>
#include <iostream>
#include <utility>
#include <algorithm>
#include <set>
#include <limits.h>
using namespace std;
#define v vector
#define pii pair<int,int>
#define fi first
#define se second
#define ll long long
 
int N,K;
v<pii> pos;
v<v<long long>> memo;
long long diagSolve(int cur, int k){//cover first cur with k photos
    if(memo[cur][k]!=-1) return memo[cur][k];
    if(cur==0) return memo[cur][k] = 0;
    if(k==0) return LLONG_MAX/2;

    long long ret=LLONG_MAX/2;
    for(int i=0;i<cur;i++){
        long long curArea=(pos[cur-1].se-pos[i].fi+1) * (pos[cur-1].se-pos[i].fi+1);
        //check for intersection with prev:
        if(i!=0){
            long long length = max(0, pos[i-1].se-pos[i].fi+1);
            curArea-=length*length;
        }

        long long take = diagSolve(i,k-1);

        if(take+curArea<ret) ret=take+curArea;
    }
    return memo[cur][k] = ret;
}

long long take_photos(int n, int m, int k, std::vector<int> r, std::vector<int> c) {
    set<pii> tmp;
    for(int i=0;i<n;i++){
        tmp.insert({min(r[i],c[i]),-max(c[i],r[i])});
    }
    for(pii it:tmp){
        if(pos.size()==0) {
            pos.push_back({it.fi,-it.se});
            continue;
        }
        if(it.fi<=pos.back().se && -it.se<=pos.back().se) continue;
        pos.push_back({it.fi,-it.se});
    }
    N=pos.size();
    K=k;
    //top down:
    //memo=v<v<ll>>(N+1,v<long long>(k+1,-1));
    //return diagSolve(N,k);

    //bottom up: for convex hull soon:
    memo=v<v<ll>>(K+1,v<ll>(N+1,-1));
    for(int i=0;i<=K;i++) memo[i][0]=0;
    for(int i=1;i<=N;i++) memo[0][i]=LLONG_MAX/2;

    for(k=1;k<=K;k++){
        for(int i=1;i<=N;i++){
            long long val=LLONG_MAX/2;
            for(int j=0;j<i;j++){
                long long curArea=(pos[i-1].se-pos[j].fi+1) * (pos[i-1].se-pos[j].fi+1);
                //check for intersection with prev:
                if(j!=0){
                    long long length = max(0, pos[j-1].se-pos[j].fi+1);
                    curArea-=length*length;
                }
                long long take = memo[k-1][j];

                if(take+curArea<val) val=take+curArea;
            }
            memo[k][i]=val;
        }
    }
    return memo[K][N];
}

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