Submission #680490

#	Time	Username	Problem	Language	Result	Execution time	Memory
680490		ngrace	Aliens (IOI16_aliens)	C++14	0 / 100	3 ms	508 KiB

aliens

#include <bits/stdc++.h>
using namespace std;
#define v vector
#define ll long long
#define ii pair<long long,long long>
#define fi first
#define se second
 
v<ii> ph;
ll C(int i, int j){ // i>j, j is exclusive.
    ll len = ph[i].se - ph[j+1].fi + 1;
    ll intersect = max(0LL, ph[j].se - ph[j+1].fi + 1);
    return len*len - intersect*intersect;   
}
 
v<ll> dplast, dpcur;
void comp(int l, int r, int optl, int optr){
    if(l>r) return;
 
    int m=(l+r)/2;
    dpcur[m] = 1e18;
    int opt;
    for(int i=optl; i<=min(m-1, optr); i++){
        ll cur = dplast[i] + C(m,i);
        if(cur<dpcur[m]){
            dpcur[m]=cur;
            opt=i;
        }
    }
    
    comp(l,m-1,optl,opt);
    comp(m+1,r,opt,optr);
}
 
 
 
long long take_photos(int n, int m, int k, std::vector<int> r, std::vector<int> c) {
    set<ii> tmp;
    for(int i=0;i<n;i++){
        tmp.insert({min(r[i],c[i]),-max(c[i],r[i])});
    }    cin.tie(0);
 
    ph.push_back({-1,-1});
    for(ii it:tmp){
        if(ph.back().se < -it.se) ph.push_back({it.fi, -it.se});
    }
    n=ph.size()-1;
 
 
    if(n<=4000){//knuths
        v<v<int>> opt(k+1, v<int>(n+2, 0));
        for(int h=0; h<=k; h++) opt[h][n+1]=n;
        v<v<ll>> dp(k+1, v<ll>(n+1, 1e18));
        for(int h=0; h<=k; h++) dp[h][0] = 0;
        for(int h=1; h<=k; h++){
            for(int i=n; i>0; i--){
                for(int j=opt[h-1][i]; j<=min(i-1, opt[h][i+1]); j++){
                    ll cost = dp[h-1][j] + C(i,j);
                    if(cost<dp[h][i]){
                        dp[h][i] = cost;
                        opt[h][i]=j;
                    }
                }
            }
        }
        cout<<dp[k][n]<<endl;
    }
    else{//d&c
        dplast = v<ll>(n+2,0);
        dpcur = v<ll>(n+2,0);
        for(int i=1; i<=n; i++) dplast[i] = C(i,0);
        for(int h=2; h<=k; h++){
            comp(1, n, 0, n);
            dplast = dpcur;
        }
        cout<<dplast[n]<<endl;
    }
}

Compilation message (stderr)

aliens.cpp: In function 'long long int take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:78:1: warning: no return statement in function returning non-void [-Wreturn-type]
   78 | }
      | ^
aliens.cpp: In function 'void comp(int, int, int, int)':
aliens.cpp:31:9: warning: 'opt' may be used uninitialized in this function [-Wmaybe-uninitialized]
   31 |     comp(l,m-1,optl,opt);
      |     ~~~~^~~~~~~~~~~~~~~~

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