Submission #367632

#	Time	Username	Problem	Language	Result	Execution time	Memory
367632		Sparky_09	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	233 ms	22508 KiB

oneway

#include "bits/stdc++.h"
using namespace std;
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define trav(a, x) for(auto& a : x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pii> vpi;

template <class T>
void rd(T &x) {
	int sgn = 1;
	char ch;
	x = 0;
	for (ch = getchar(); (ch < '0' || ch > '9') && ch != '-'; ch = getchar()) ;
	if (ch == '-') ch = getchar(), sgn = -1;
	for (; '0' <= ch && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';
	x *= sgn;
}
template <class T>
void wr(T x) {
	if (x < 0) putchar('-'), wr(-x);
	else if (x < 10) putchar(x + '0');
	else wr(x / 10), putchar(x % 10 + '0');
}

template<class T> bool ckmin(T& a, const T& b) { return a > b ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }

void usaco(string s){
  freopen((s+".in").c_str(), "r", stdin);
  freopen((s+".out").c_str(), "w", stdout);
}

pii node[100010];
vector<pii> edge[100010], e[100010];
int n, m, disc[100010], low[100010], tot, stck[100010], tp, color[100010], cnt, w[100010];
bool proc[100010];
char ans[100010];

void tarjan(int x, int id){
    disc[x] = low[x] = ++tot;
    stck[++tp] = x;
    proc[x] = 1;
    for(auto p: edge[x]){
        int y = p.first;
        if(p.second == id)
            continue;
        if(!disc[y]){
            tarjan(y, p.second);
            low[x] = min(low[x], low[y]);
        } 
        else if(proc[y])
            low[x] = min(low[x], disc[y]);
    }
    if(disc[x] == low[x]){
        int y;
        ++cnt;
        do{
            y = stck[tp--];
            proc[y] = 0;
            color[y] = cnt;
        }while(y != x);
    }
}


void dfs(int x, int fa){
    disc[x] = -1;
    for(auto p: e[x]){
        int y = p.first, id = p.second;
        if(y == fa)
            continue;
        dfs(y, x);
        w[x] += w[y];
        if(!w[y])
            ans[id] = 'B';
        else if(w[y] > 0)
            ans[id] = (node[id] == pii(y, x)) ? 'R' : 'L';
        else
            ans[id] = (node[id] == pii(x, y)) ? 'R' : 'L';
    }
}


int main() {
#ifdef LOCAL_DEFINE
	freopen("input.txt", "r", stdin);
#endif
    cin >> n >> m;
    int x, y;
    for(int i = 1; i <= m; i++){
        cin >> x >> y;
        node[i] = pii(x, y);
        edge[x].push_back(pii(y, i));
        edge[y].push_back(pii(x, i));
    }
    for(int i = 1; i <= n; i++)
        if (!disc[i])
            tarjan(i, 0);
    for (int i = 1; i <= m; i++){
        if (color[node[i].first] == color[node[i].second]){
            ans[i] = 'B';
            continue;
        }
        x = color[node[i].first], y = color[node[i].second];
        e[x].push_back(pii(y, i));
        e[y].push_back(pii(x, i));
        node[i] = pii(x, y);
    }
    int qq;
    cin >> qq;
    while(qq--){
        cin >> x >> y;
        if(color[x] == color[y]) continue;
        x = color[x], y = color[y];
        w[x]++, w[y]--;
    }
    for(int i = 1; i <= n; i++)
        if(disc[i] >= 0)
            dfs(i, 0);
    for(int i = 1; i <= m; i++) cout << ans[i];
}

Compilation message (stderr)

oneway.cpp: In function 'void usaco(std::string)':
oneway.cpp:33:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   33 |   freopen((s+".in").c_str(), "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:34:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   34 |   freopen((s+".out").c_str(), "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 30 / 30
• Subtask 2: 30 / 30
• Subtask 3: 40 / 40