Submission #666859

#TimeUsernameProblemLanguageResultExecution timeMemory
666859LoboAliens (IOI16_aliens)C++17
60 / 100
1666 ms1048576 KiB
#include<bits/stdc++.h>
#include "aliens.h"
using namespace std;
#define int long long
#define dbl long double
#define fr first
#define sc second
#define mp make_pair
#define pb push_back
#define all(x) x.begin(),x.end()
const int inf = 1e18+10;
int n;
vector<pair<int,int>> pts;

deque<pair<int,int>> cht;

dbl intx(int a1, int b1, int a2, int b2) {
    // x*a1 + b1 = x*a2 + b2
    // x*(a1-a2) = b2-b1
    // x = (b2-b1)/(a1-a2)
    return ((dbl) b2-b1)/((dbl) a1-a2);
}

int func(int a, int b, int x) {
    return a*x+b;
}

void chtclear() {
    cht.clear();
}

void chtadd(int a, int b) {
    while(cht.size() >= 2 && intx(a,b,cht[1].fr,cht[1].sc) >= intx(cht[0].fr,cht[0].sc,cht[1].fr,cht[1].sc)) {
        cht.pop_front();
    }
    cht.push_front(mp(a,b));
}

int chtqry(int x) {
    while(cht.size() >= 2 && func(cht.back().fr,cht.back().sc,x) >= func(cht[cht.size()-2].fr,cht[cht.size()-2].sc,x)) {
        cht.pop_back();
    }
    return func(cht.back().fr,cht.back().sc,x);
}

int sol(int K) {
    int dp[n][K+1];
    for(int i = 0; i < n; i++) dp[i][0] = inf;

    for(int k = 1; k <= K; k++) {
        chtclear();
        for(int i = 0; i < n; i++) {
            dp[i][k] = inf;
            int xi = pts[i].fr;
            int yi = pts[i].sc;

            if(i == 0) {
                int xj = pts[i].fr;
                int yj = pts[i].sc;
                chtadd(yj,yj*yj - 2*yj);
            }
            else {
                int j = i;
                int xj = pts[i].fr;
                int yj = pts[i].sc;
                int xj1 = pts[i-1].fr;
                int yj1 = pts[i-1].sc;
                chtadd(yj,(dp[j-1][k-1] + yj*yj - 2*yj - max((int)0,xj1-yj+1)*max((int) 0,xj1-yj+1)));
            }

            dp[i][k] = chtqry(-2*xi)+(xi*xi + 2*xi + 1);

            // cout << i << " " << k << " " << dp[i][k] << endl;
            // for(int j = 0; j <= i; j++) {
            //     int xj = pts[j].fr;
            //     int yj = pts[j].sc;
            //     if(j == 0) {
            //         dp[i][k] = min(dp[i][k], (xi*xi + 2*xi + 1) + (yj*yj - 2*yj)  + (- 2*xi*yj));
            //     }
            //     else {
            //         int xj1 = pts[j-1].fr;
            //         int yj1 = pts[j-1].sc;
            //         dp[i][k] = min(dp[i][k] ,(xi*xi + 2*xi + 1) + (dp[j-1][k-1] + yj*yj - 2*yj - max((int)0,xj1-yj+1)*max((int) 0,xj1-yj+1))  + (- 2*xi*yj));
            //     }
            // }
        }
    }
    return dp[n-1][K];
}

// int sol(int K) {
//     int dp[n][K+1];
//     for(int i = 0; i < n; i++) dp[i][0] = inf;

//     for(int k = 1; k <= K; k++) {
//         for(int i = 0; i < n; i++) {
//             dp[i][k] = inf;
//             int xi = pts[i].fr;
//             int yi = pts[i].sc;
//             for(int j = 0; j <= i; j++) {
//                 int xj = pts[j].fr;
//                 int yj = pts[j].sc;
//                 if(j == 0) {
//                     dp[i][k] = min(dp[i][k], (xi*xi + 2*xi + 1) + (yj*yj - 2*yj)  + (- 2*xi*yj));
//                 }
//                 else {
//                     int xj1 = pts[j-1].fr;
//                     int yj1 = pts[j-1].sc;
//                     dp[i][k] = min(dp[i][k] ,(xi*xi + 2*xi + 1) + (dp[j-1][k-1] + yj*yj - 2*yj - max((int)0,xj1-yj+1)*max((int) 0,xj1-yj+1))  + (- 2*xi*yj));
//                 }
//             }
//         }
//     }
//     return dp[n-1][K];
// }

int take_photos(int32_t N, int32_t m, int32_t k, vector<int32_t> r, vector<int32_t> c) {
    for(int i = 0; i < N; i++) {
        int x = c[i];
        int y = r[i];
        if(x < y) swap(x,y);
        pts.pb(mp(x,-y));
    }

    sort(all(pts));

    stack<pair<int,int>> prt;
    for(auto X : pts) {
        int x = X.fr;
        int y = -X.sc;

        while(prt.size() && prt.top().sc >= y) prt.pop();
        prt.push(mp(x,y));
    }
    pts.clear();
    while(prt.size()) {
        pts.pb(prt.top());
        prt.pop();
    }
    sort(all(pts));
    n = pts.size();

    return sol(k);
}

Compilation message (stderr)

aliens.cpp: In function 'long long int sol(long long int)':
aliens.cpp:58:21: warning: unused variable 'xj' [-Wunused-variable]
   58 |                 int xj = pts[i].fr;
      |                     ^~
aliens.cpp:64:21: warning: unused variable 'xj' [-Wunused-variable]
   64 |                 int xj = pts[i].fr;
      |                     ^~
aliens.cpp:67:21: warning: unused variable 'yj1' [-Wunused-variable]
   67 |                 int yj1 = pts[i-1].sc;
      |                     ^~~
aliens.cpp:55:17: warning: unused variable 'yi' [-Wunused-variable]
   55 |             int yi = pts[i].sc;
      |                 ^~
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