Submission #134888

#	Time	Username	Problem	Language	Result	Execution time	Memory
134888		onjo0127	Telegraph (JOI16_telegraph)	C++11	100 / 100	67 ms	15476 KiB

telegraph

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

const long long INF = 1LL * 1e18;
int N, A[100009], C[100009], D[100009], vs[100009];
bool fin[100009];
vector<vector<int> > R;
vector<int> T[100009];
long long ans;

void go(vector<int> &S, int x, int c) {
	S.push_back(x);
	vs[x] = c;
	if(vs[A[x]]) {
		if(!fin[x] && vs[A[x]] == c) {
			vector<int> stk;
			while(1) {
				int tmp = S.back(); S.pop_back();
				stk.push_back(tmp);
				if(tmp == A[x]) break;
			}
			for(auto& it: stk) fin[it] = 1;
			reverse(stk.begin(), stk.end());
			R.push_back(stk);
		}
	}
	else go(S, A[x], c);
}

void dfs(int x) {
	D[x] = 0;
	long long s = 0;
	for(auto& it: T[x]) {
		dfs(it);
		D[x] = max(D[x], C[it]);
		s += C[it];
	}
	ans += s - D[x];
}

int main() {
	scanf("%d",&N);
	for(int i=1; i<=N; i++) scanf("%d%d",&A[i],&C[i]);
	for(int i=1; i<=N; i++) if(!vs[i]) {
		vector<int> S;
		go(S, i, i);
	}
		
	// printf("rings: %d\n", R.size());
	// for(auto& it: R) {
	// 	puts("ring");
	// 	for(auto& jt: it) printf("%d ",jt);
	// 	puts("");
	// }
	// puts("\n");

	bool f = 1;
	for(int i=1; i<=N; i++) if(!fin[i]) {
		// printf("tree edge: %d -> %d\n", A[i], i);
		T[A[i]].push_back(i);
		f = 0;
	}
	if(f && (int)R.size() == 1) return !printf("0");
	for(int i=1; i<=N; i++) if(fin[i]) dfs(i);
	for(auto& it: R) {
		long long mn = INF, s = 0;
		int pr = it.back();
		for(int i=0; i<it.size(); i++) {
			s += min(C[pr], D[it[i]]);
			pr = it[i];
		}
		for(int i=0; i<it.size(); i++) {
			s -= min(C[pr], D[it[i]]);
			mn = min(mn, s + C[pr]);
			s += min(C[pr], D[it[i]]);
			pr = it[i];
		}
		ans += mn;
	}
	printf("%lld", ans);
	return 0;
}

Compilation message (stderr)

telegraph.cpp: In function 'int main()':
telegraph.cpp:68:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0; i<it.size(); i++) {
                ~^~~~~~~~~~
telegraph.cpp:72:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0; i<it.size(); i++) {
                ~^~~~~~~~~~
telegraph.cpp:42:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&N);
  ~~~~~^~~~~~~~~
telegraph.cpp:43:31: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(int i=1; i<=N; i++) scanf("%d%d",&A[i],&C[i]);
                          ~~~~~^~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 30 / 30
• Subtask 3: 30 / 30
• Subtask 4: 30 / 30