Submission #1245302

#	Time	Username	Problem	Language	Result	Execution time	Memory
1245302		Boomyday	Wiring (IOI17_wiring)	C++20	0 / 100	24 ms	8952 KiB

wiring

//
// Created by adavy on 7/22/2025.
//
#include <bits/stdc++.h>
#include "wiring.h"
using namespace std;

using ll = long long;

const ll INF = 1e13;
// somehow seperate into consecutive blocks of R, B, R, B, R, B, ...
// do DP with 2 pointers
// do dp on prefixes for simplicity

long long calc_score(ll num_back, ll num_front, ll sum_back, ll sum_front, ll max_back, ll min_front){
    return sum_front - sum_back - max(0LL, num_front-num_back)*max_back + max(0LL, num_back-num_front)*min_front;
}

long long min_total_length(std::vector<int> r, std::vector<int> b) {
    vector<vector<int>> blocks;
    vector<int> nums;

    int rptr = 0, bptr = 0;
    vector<int> curblock;
    while (rptr < r.size() || bptr < b.size()){
        curblock.clear();
        while(bptr == b.size() || r[rptr] < b[bptr]){
            curblock.push_back(r[rptr++]);
            if (rptr == r.size()) break;
        }
        if (!curblock.empty()) blocks.push_back(curblock);
        if (bptr == b.size() && rptr==r.size()) break;
        curblock.clear();

        while(rptr == r.size() || b[bptr] < r[rptr]){
            curblock.push_back(b[bptr++]);
            if (bptr == b.size()) break;

        }
        if (!curblock.empty()) blocks.push_back(curblock);
    }
    /*
    for(auto&block:blocks){
        for(auto&x:block) cout << x << " ";
        cout << endl;
    }*/
    for(auto&block:blocks) for(auto&x:block) nums.push_back(x);
    vector<ll> dp = {0}; // dp[i] = first i counters have been placed down
    int i=0;
    for(int j=0;j<blocks.size();++j){

        if (j==0) {
            for(int k=0;k<blocks[j].size();++k,++i) dp.push_back(INF*(k+1));
            continue;
        }
        int cur_back = i-1;
        int sum_back = nums[cur_back];
        int far_back = i-blocks[j-1].size(); // can't go further back than this
        int num_back = 1;
        int num_front, sum_front = 0;
        int max_back = nums[i-1];
        int min_front = nums[i];


        for(int k=0;k<blocks[j].size();++k,++i){
            num_front = k + 1; sum_front += nums[i];
            ll best_score = dp[cur_back] + calc_score(num_back, num_front, sum_back, sum_front, max_back, min_front);
            //cout << i << " " << num_back << " " << num_front << " " << sum_back << " " << sum_front << " " << max_back << " " << min_front << endl;
            // update back
            while (cur_back > far_back){
                ll new_score = dp[cur_back-1] + calc_score(num_back+1, num_front, sum_back + nums[cur_back-1], sum_front, max_back, min_front);
                if (new_score < best_score){
                    best_score = new_score;
                    sum_back += nums[cur_back - 1];
                    cur_back--;
                    num_back++;

                }
                else{
                    break;
                }
            }
            dp.push_back(best_score);
            //cout << i+1 << " " << dp[i+1] << endl;

        }
    }
    return dp.back();
}

• Subtask 1: 0 / 7
• Subtask 2: 0 / 13
• Subtask 3: 0 / 10
• Subtask 4: 0 / 25
• Subtask 5: 0 / 45