Submission #43041

#	Time	Username	Problem	Language	Result	Execution time	Memory
43041		top34051	Aliens (IOI16_aliens)	C++14	4 / 100	4 ms	3036 KiB

aliens

#include "aliens.h"
#include<bits/stdc++.h>
using namespace std;

#define ll long long
#define pii pair<ll,ll>
#define X first
#define Y second
const int maxn = 1e5 + 5;

struct line {
    ll m,c,id;
    line(ll _m = 0, ll _c = 0, int _id = 0) {
        m = _m; c = _c; id = _id;
    }
};

int n,m,k;
pii p[maxn];
int r[maxn], c[maxn];
ll dp[maxn];
int cnt[maxn];
line cht[maxn];

bool cmp(pii x, pii y) {
    if(x.X!=y.X) return x.X<y.X;
    return x.Y>y.Y;
}

ll p2(ll x) { return x*x; }

double cut(int x, int y) {
    if(x==0 || y==0) return -2e16;
    return (double)(cht[y].c-cht[x].c)/(cht[x].m-cht[y].m);
}

int solve(ll cost) {
    int len = 0;
    for(int x=1;x<=n;x++) {
        cht[++len] = line(-2*r[x], p2(r[x]) + dp[x-1] - p2(max(0,c[x-1]-r[x])),x-1);
        while(len>=3 && cut(len-1,len)<cut(len-2,len)) cht[len-1] = cht[len], len--;
        int l = 2, r = len, mid, pos = 1;
        while(l<=r) {
            int mid = (l+r)/2;
            if(cut(mid-1,mid)<=c[x]) pos = mid, l = mid+1;
            else r = mid-1;
        }
        dp[x] = cht[pos].m*c[x] + cht[pos].c + p2(c[x]) + cost;
        cnt[x] = cnt[cht[pos].id] + 1;
//        printf("dp %d %d = %lld\n",x,t,dp[x][t]);
    }
    return cnt[n];
}

long long take_photos(int N, int M, int K, std::vector<int> R, std::vector<int> C) {
	n = N; m = M; k = K;
	//prep
	for(int i=0;i<n;i++) {
        p[i] = {R[i],C[i]};
        if(p[i].X>p[i].Y) swap(p[i].X,p[i].Y);
	}
	sort(p,p+n,cmp);
    ll cur = -1, sz = 0;
	for(int i=0;i<n;i++) {
        if(p[i].Y<=cur) continue;
        sz++;
        r[sz] = p[i].X; c[sz] = p[i].Y+1;
        cur = p[i].Y;
	}
	n = sz;
	//bsearch
	ll l = 0, r = 1e13, mid, pos;
	while(l<=r) {
        mid = (l+r)/2;
        if(solve(mid)<=k) pos = mid, r = mid-1;
        else l = mid+1;
	}
	solve(pos);
    return dp[n] - pos*k;
}

Compilation message (stderr)

aliens.cpp: In function 'int solve(long long int)':
aliens.cpp:42:29: warning: unused variable 'mid' [-Wunused-variable]
         int l = 2, r = len, mid, pos = 1;
                             ^
aliens.cpp: In function 'long long int take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:78:12: warning: 'pos' may be used uninitialized in this function [-Wmaybe-uninitialized]
  solve(pos);
            ^

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