Submission #56740

#	Time	Username	Problem	Language	Result	Execution time	Memory
56740		RezwanArefin01	Ideal city (IOI12_city)	C++17	100 / 100	453 ms	24628 KiB

city

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

const int mod = 1e9; 
const int M = 1e5 + 10; 

int dx[] = {1, -1, 0, 0}; 
int dy[] = {0, 0, -1, 1}; 
vector<int> adj[M]; 
int comp[M], w[M], sub[M]; 
int ans = 0; 

void dfs(int u, int par) {
	sub[u] = w[u];
	for(int v : adj[u]) if(v - par) {
		dfs(v, u); 
		sub[u] += sub[v];
		if(sub[u] >= mod) 
			sub[u] -= mod; 
	}
}

void solve(int N, int *X, int *Y) {
	vector<pair<int, int> > v; 
    map<pair<int, int>, int> mp; 

    for(int i = 0; i < N; i++) 
        v.emplace_back(X[i], Y[i]); 
    sort(v.begin(), v.end()); 

    for(int i = 0; i < N; i++) 
    	mp[{v[i].first, v[i].second}] = i; 

    int idx = 0; 
    for(int i = 0; i < N; ) {
        int x = v[i].first, j = i + 1; 
        comp[i] = idx; 
        while(j < N && v[j].second == v[j - 1].second + 1)
            comp[j++] = idx; 
        w[idx++] = j - i;
        i = j;  
    }
    
    set<pair<int, int> > st; 
    for(int i = 0; i < N; i++) {
        int x = v[i].first, y = v[i].second; 
        for(int j = 0; j < 4; j++) {
            int xx = x + dx[j], yy = y + dy[j];
            if(mp.count({xx, yy})) {
                int a = comp[i], b = comp[mp[{xx, yy}]]; 
                if(a > b) swap(a, b); 
                if(a != b) st.insert({a, b}); 
            }
        }
    }
    for(int i = 0; i < idx; i++) 
        adj[i].clear(); 
    
    for(auto it : st) {
        int u = it.first, v = it.second; 
       	adj[u].push_back(v);
        adj[v].push_back(u); 
    }	

    dfs(0, -1); 

    for(int i = 1; i < idx; i++) {
    	ans += sub[i] * 1ll * (N - sub[i]) % mod; 
    	if(ans >= mod) ans -= mod; 
    }
}

int DistanceSum(int N, int *X, int *Y) {
	solve(N, X, Y);
	solve(N, Y, X); 
	return ans; 
}

Compilation message (stderr)

city.cpp: In function 'void solve(int, int*, int*)':
city.cpp:36:13: warning: unused variable 'x' [-Wunused-variable]
         int x = v[i].first, j = i + 1; 
             ^

• Subtask 1: 11 / 11
• Subtask 2: 21 / 21
• Subtask 3: 23 / 23
• Subtask 4: 45 / 45