Submission #1302517

#	Time	Username	Problem	Language	Result	Execution time	Memory
1302517		regulardude6	Triple Peaks (IOI25_triples)	C++20	0.51 / 100	23 ms	23580 KiB

triples

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

long long count_triples(vector<int> H){
    int n = (int)H.size();
    vector<vector<int>> L(n), R(n);
    for(int i=0;i<n;i++){
        int a = H[i];
        if(i + a < n) L[i + a].push_back(a);
        if(i - a >= 0) R[i - a].push_back(a);
    }

    long long ans = 0;

    for(int i=0;i<n;i++){
        int d = H[i];
        int k = i + d;
        if(k >= n) continue;
        int t = H[k];
        if(1 <= t && t <= d-1){
            int j1 = i + t;
            if(j1 > i && j1 < k && H[j1] == d - t) ans++;
            int j2 = i + (d - t);
            if(j2 > i && j2 < k && j2 != j1 && H[j2] == t) ans++;
        }
    }

    for(int k=0;k<n;k++){
        int d = H[k];
        int i = k - d;
        if(i < 0) continue;
        int t = H[i];
        if(1 <= t && t <= d-1){
            int j1 = i + t;
            if(j1 > i && j1 < k && H[j1] == d - t) ans++;
            int j2 = i + (d - t);
            if(j2 > i && j2 < k && j2 != j1 && H[j2] == t) ans++;
        }
    }

    for(int j=0;j<n;j++){
        int d = H[j];
        auto &A = L[j];
        auto &B = R[j];
        if(A.empty() || B.empty()) continue;

        if((int)A.size() <= (int)B.size()){
            unordered_set<int> sb;
            sb.reserve(B.size() * 2 + 1);
            for(int x: B) sb.insert(x);
            for(int a: A){
                int b = d - a;
                if(b >= 1 && b <= n-1 && sb.find(b) != sb.end()) ans++;
            }
        }else{
            unordered_set<int> sa;
            sa.reserve(A.size() * 2 + 1);
            for(int x: A) sa.insert(x);
            for(int b: B){
                int a = d - b;
                if(a >= 1 && a <= n-1 && sa.find(a) != sa.end()) ans++;
            }
        }
    }

    return ans;
}

vector<int> construct_range(int M, int K){
    int N = max(3, min(M, 200000));
    vector<int> H(N, 1);
    if(N >= 3) H[2] = 2;
    return H;
}

• Subtask 0: 0 / 0
• Subtask 1: 0 / 8
• Subtask 2: 0 / 6
• Subtask 3: 0 / 10
• Subtask 4: 0 / 11
• Subtask 5: 0 / 16
• Subtask 6: 0 / 19
• Subtask 7: 0.5 / 5
• Subtask 8: 0.0075 / 5
• Subtask 9: 0.0003 / 5
• Subtask 10: 0 / 5
• Subtask 11: 0 / 5
• Subtask 12: 0 / 5