Submission #961765

#	Time	Username	Problem	Language	Result	Execution time	Memory
961765		Ahmed57	Aliens (IOI16_aliens)	C++17	100 / 100	165 ms	9036 KiB

aliens

#include <bits/stdc++.h>
#include "aliens.h"

using namespace std;
struct line {
    long long m, c, z;
};
struct CHT {
    long long la = -1 , ma = 0;
    deque <line> lines;
    CHT(){
        la = -1;
        ma = 0;
    }
    bool cmp(const pair <long long, long long> &x, const pair <long long,long long> &y) {
        return (x.first) * (y.second) < (x.second) * (y.first);
    }
    bool equ(const pair <long long, long long> &x, const pair <long long,long long> &y) {
        return (x.first) * (y.second) == (x.second) * (y.first);
    }
    void push(line x) {
        if(lines.size() && lines.back().m == x.m) {
            if(x.c == lines.back().c){
                if(x.z<lines.back().z)return ;
                else lines.pop_back();
            }else{
                if(x.c < lines.back().c) lines.pop_back();
                else return;
            }
        }
        while(lines.size() >= 2 && cmp({lines.back().c - x.c, x.m - lines.back().m}, {lines[lines.size() - 2].c - lines.back().c, lines.back().m - lines[lines.size() - 2].m})) lines.pop_back();
        lines.push_back(x);
    }
    pair<long long,long long> query(long long x) {
        if(x!=la){
            la = x;
            ma = 0;
        }
        while(lines.size() >= 2 && !(cmp({x,1},{lines[1].c - lines[0].c, lines[0].m - lines[1].m}))){
            if(equ({x,1},{lines[1].c - lines[0].c, lines[0].m - lines[1].m})){
                ma = max(ma,lines[0].z);
            }
            lines.pop_front();
        }
        return {lines[0].m * x + lines[0].c, max(ma,lines[0].z)};
    }
};
long long take_photos(int n, int m, int k, vector<int> r,vector<int> c){
    vector<pair<long long,long long>> seg1,seg;
    for(int i = 0;i<n;i++){
        seg1.push_back({min(c[i],r[i]),max(c[i],r[i])});
    }
    sort(seg1.begin(),seg1.end());
    long long ma = -1e18;
    for(int i = 0;i<n;i++){
        if(seg1[i].second>ma){
            seg.push_back(seg1[i]);
            ma = seg1[i].second;
        }
    }
    long long L = 0 , R = 1e12 , all = 0;
    k = min(k,(int)seg.size());
    while(L<=R){
        long long mid = (L+R)/2;
        pair<long long,long long> dp[seg.size()+1];
        dp[0] = {0,0};
        CHT cht;
        for(int i = 1;i<=seg.size();i++){
            int e = i-1;
            line pu = {(-2)*seg[e].first,dp[e].first+seg[e].first*seg[e].first-2*seg[e].first+1-(e==0?0:max(0ll,seg[e-1].second-seg[e].first+1)*max(0ll,seg[e-1].second-seg[e].first+1)),dp[e].second};
            cht.push(pu);
            dp[i] = cht.query(seg[i-1].second);
            dp[i].first+=seg[i-1].second*seg[i-1].second+2*seg[i-1].second+mid;
            dp[i].second++;
        }
        if(dp[seg.size()].second>=k){
            all = dp[seg.size()].first-(mid*k);
            L = mid+1;
        }else R = mid-1;
    }
    return all;
    
}

Compilation message (stderr)

aliens.cpp: In function 'long long int take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:68:24: 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]
   68 |         for(int i = 1;i<=seg.size();i++){
      |                       ~^~~~~~~~~~~~

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