Submission #680488

#	Time	Username	Problem	Language	Result	Execution time	Memory
680488		ngrace	Aliens (IOI16_aliens)	C++14	Compilation error	0 ms	0 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);
}



int main(){
    cin.tie(0);
    iostream::sync_with_stdio(0);

    ll n,m,K;
    cin>>n>>m>>K;//n points, mxm grid, k photo's allowed

    set<ii> tmp;
    //min photo needed per point represented as min(a,b), max(a,b) points on diagonal.
    for(int i=0; i<n; i++){
        int a,b;
        cin>>a>>b;
        tmp.insert({min(a,b),-max(a,b)});
    }
    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 k=0; k<=K; k++) opt[k][n+1]=n;
        v<v<ll>> dp(K+1, v<ll>(n+1, 1e18));
        for(int k=0; k<=K; k++) dp[k][0] = 0;
        for(int k=1; k<=K; k++){
            for(int i=n; i>0; i--){
                for(int j=opt[k-1][i]; j<=min(i-1, opt[k][i+1]); j++){
                    ll cost = dp[k-1][j] + C(i,j);
                    if(cost<dp[k][i]){
                        dp[k][i] = cost;
                        opt[k][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 k=2; k<=K; k++){
            comp(1, n, 0, n);
            dplast = dpcur;
        }
        cout<<dplast[n]<<endl;
    }
}

Compilation message (stderr)

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);
      |     ~~~~^~~~~~~~~~~~~~~~
/usr/bin/ld: /tmp/cc9r69om.o: in function `main':
grader.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/cct1Odvo.o:aliens.cpp:(.text.startup+0x0): first defined here
/usr/bin/ld: /tmp/cc9r69om.o: in function `main':
grader.cpp:(.text.startup+0xf0): undefined reference to `take_photos(int, int, int, std::vector<int, std::allocator<int> >, std::vector<int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status