Submission #1259121

#	Time	Username	Problem	Language	Result	Execution time	Memory
1259121		Aviansh	Triple Peaks (IOI25_triples)	C++20	75.29 / 100	999 ms	27976 KiB

triples

#include "triples.h"

#include <bits/stdc++.h>

using namespace std;

bool checkTriple(int i, int j, int k, vector<int>&arr){
    if(!(i<j&&j<k)){
        return 0;
    }
    int n = arr.size();
    if(i<0||j<0||k<0||i>=n||j>=n||k>=n){
        return 0;
    }
    vector<int>arr1 = {j-i,k-i,k-j};
    vector<int>arr2 = {arr[i],arr[j],arr[k]};
    sort(arr1.begin(),arr1.end());
    sort(arr2.begin(),arr2.end());
    if(arr1[0]==arr2[0]&&arr1[1]==arr2[1]&&arr1[2]==arr2[2]){
        return 1;
    }
    return 0;
}

long long count_triples(vector<int> arr) {
    int n = arr.size();
    set<array<int,3>>triples;
    vector<vector<int>>mp(4e5+5);
    int off = 2e5+1;
    for(int i = 0;i<n;i++){
        mp[arr[i]-i+off].push_back(i);
    }
    for(int i = 0;i<n;i++){
        int a,b,c;
        //case 1:
        a = i;
        b = arr[a]+a;
        if(b>=0&&b<n)
            c = arr[b]+a;
        if(checkTriple(a,b,c,arr)){
            triples.insert({a,b,c});
        }
        //case 2:
        a=i;
        c=arr[a]+a;
        if(c>=0&&c<n)
            b=c-arr[c];
        if(checkTriple(a,b,c,arr)){
            triples.insert({a,b,c});
        }
        //case 3:
        a=i;
        c=arr[a]+a;
        if(c>=0&&c<n)
            b=arr[c]+a;
        if(checkTriple(a,b,c,arr)){
            triples.insert({a,b,c});
        }
        //case 4:
        a=i;
        b=arr[a]+a;
        if(b>=0&&b<n)
            c=arr[b]+b;
        if(checkTriple(a,b,c,arr)){
            triples.insert({a,b,c});
        }
        //case 5:
        //later

        //case 6:
        b=i;
        a=b-arr[b];
        if(a>=0&&a<n)
            c=arr[a]+b;
        if(checkTriple(a,b,c,arr)){
            triples.insert({a,b,c});
        }
    }
    int lim = sqrt(n);
    int ans = 0;
    for(int z = 0;z<4e5+5;z++){
        pair<int,vector<int>>p = {z,mp[z]};
        int siz = p.second.size();
        if(siz>lim)
            continue;
        for(int i = 0;i<siz;i++){
            for(int j = i+1;j<siz;j++){
                int a = p.second[i];
                int b = p.second[j];
                int c = arr[b]+a;
                if(c-b==b-a)
                    continue;
                if(checkTriple(a,b,c,arr)){
                    ans++;
                }
            }
        }
    }
    for(int z = 0;z<4e5+5;z++){
        pair<int,vector<int>>p = {z,mp[z]};
        int siz = p.second.size();
        if(siz<=lim)
            continue;
        int x = p.first-off;
        for(int c = 0;c<n;c++){
            int a = (c-x-arr[c])/2;
            int b = (arr[c]+c-x)/2;
            if(c-b==b-a)
                continue;
            if(checkTriple(a,b,c,arr)){
                ans++;
            }
        }
    }
    return triples.size()+ans;
}

vector<int> construct_range(int n, int K) {
    vector<int>arr(n);
    arr[0]=1;
    iota(arr.begin()+1,arr.end(),1);
    return arr;
}

• Subtask 0: 0 / 0
• Subtask 1: 8 / 8
• Subtask 2: 6 / 6
• Subtask 3: 10 / 10
• Subtask 4: 11 / 11
• Subtask 5: 16 / 16
• Subtask 6: 19 / 19
• Subtask 7: 3 / 5
• Subtask 8: 1.245 / 5
• Subtask 9: 0.4998 / 5
• Subtask 10: 0.2143 / 5
• Subtask 11: 0.25 / 5
• Subtask 12: 0.0833 / 5