oj.uz

Submission #318485

# Submission time Handle Problem Language Result Execution time Memory
318485 2020-11-02T05:40:59 Z jhnah917 Alternating Current (BOI18_alternating) C++14
0 / 100
 169 ms 16484 KB 
#include <bits/stdc++.h>
#define x first
#define y second
#define all(v) v.begin(), v.end()
#define compress(v) sort(all(v)), v.erase(unique(all(v)), v.end())
using namespace std;

typedef long long ll;

int par[101010];
vector<int> g[101010];
int find(int v){ return v == par[v] ? v : par[v] = find(par[v]); }
void merge(int pa, int ch){ pa = find(pa); ch = find(ch); if(pa != ch) par[ch] = pa; }

struct Seg{
    int tree[1 << 18], tmp[1 << 18], n;
    void init(int _n){ n = _n; memset(tree, 0, sizeof tree); memset(tmp, 0, sizeof tree); }
    void push(int node, int s, int e){
        if(!tmp[node]) return;
        tree[node] += tmp[node];
        if(s != e){
            tmp[node << 1] += tmp[node];
            tmp[node << 1 | 1] += tmp[node];
        }
        tmp[node] = 0;
    }
    void update(int node, int s, int e, int l, int r, int v){
        push(node, s, e);
        if(r < s || e < l) return;
        if(l <= s && e <= r){
            tmp[node] += v; push(node, s, e);
            return;
        }
        int m = s + e >> 1;
        update(node << 1, s, m, l, r, v);
        update(node << 1 | 1, m+1, e, l, r, v);
        tree[node] = min(tree[node << 1], tree[node << 1 | 1]);
    }
    int query(int node, int s, int e, int l, int r){
        push(node, s, e);
        if(r < s || e < l) return 1e9;
        if(l <= s && e <= r) return tree[node];
        int m = s + e >> 1;
        int t1 = query(node << 1, s, m, l, r);
        int t2 = query(node << 1 | 1, m+1, e, l, r);
        return min(t1, t2);
    }
    void update(int s, int e, int x){
        if(e >= n) e -= n;
        if(s <= e) update(1, 0, n-1, s, e, x);
        else update(1, 0, n-1, 0, e, x), update(1, 0, n-1, s, n-1, x);
    }
    int query(){ return query(1, 0, n-1, 0, n-1); }
} seg[2];

struct Info{
    int s, e, x, eli, color;
    Info() : Info(0, 0, 0) {}
    Info(int s, int e, int x) : s(s), e(e), x(x), eli(-1), color(-1) {}
    bool operator < (const Info &t) const { return make_pair(s, -e) < make_pair(t.s, -t.e); }
};

int n, m, ed, ed_idx;
Info a[101010];
vector<Info> v;

void calc_elimination(){
    deque<Info> dq;
    sort(a+1, a+m+1);
    for(int i=1; i<=m; i++){
        if(dq.empty() || dq.back().e <= a[i].e) dq.push_back(a[i]);
        else a[i].eli = dq.back().x;
    }
    while(dq.size() && dq.front().e <= ed) a[dq[0].x].eli = ed_idx, dq.pop_front();
    for(auto i : dq) v.push_back(i);
    
    iota(par, par+101010, 0);
    for(int i=1; i<=m; i++) if(a[i].eli != -1) merge(a[i].eli, a[i].x);
    for(int i=1; i<=m; i++){
        if(a[i].eli != -1) a[i].eli = find(a[i].x), g[a[i].eli].push_back(a[i].x);
        else g[a[i].x].push_back(a[i].x);
    }
}

inline bool eval(){ return seg[0].query() > 0 && seg[1].query() > 0; }

void even(){
    seg[0].init(n); seg[1].init(n);
    
    for(int i=0; i<v.size(); i++) a[v[i].x].color = i % 2;
    for(int i=1; i<=m; i++) if(a[i].color == -1) a[i].color = !a[a[i].eli].color;
    
    for(int i=1; i<=m; i++){
        seg[a[i].color].update(a[i].s, a[i].e, 1);
    }
    if(eval()){
        for(int i=1; i<=m; i++) cout << a[i].color;
    }
    else cout << "impossible";
}

void odd(){
    seg[0].init(n); seg[1].init(n);
    for(int i=0; i<v.size(); i++) a[v[i].x].color = i % 2;
    for(int i=1; i<=m; i++) if(a[i].color == -1) a[i].color = !a[a[i].eli].color;
    for(int i=1; i<=m; i++){
        seg[a[i].color].update(a[i].s, a[i].e, 1);
    }
    if(eval()){ for(int j=1; j<=m; j++) cout << a[j].color; return; }
    
    for(int i=0; i<v.size(); i++){
        for(auto j : g[v[i].x]){
            seg[a[j].color].update(a[j].s, a[j].e, -1);
            a[j].color ^= 1;
            seg[a[j].color].update(a[j].s, a[j].e, 1);
        }
        if(eval()){ for(int j=1; j<=m; j++) cout << a[j].color; return; }
    }
    cout << "impossible";
}

int main(){
    ios_base::sync_with_stdio(false); cin.tie(nullptr);
    cin >> n >> m;
    for(int i=1; i<=m; i++){
        int s, e; cin >> s >> e; s--; e--;
        if(s > e){
            if(ed < e) ed = e, ed_idx = i;
            e += n;
        }
        a[i] = {s, e, i};
    }
    calc_elimination();
    sort(a+1, a+m+1, [](Info a, Info b){ return a.x < b.x; });
    if(v.size() % 2 == 0) even();
    else odd();
}

Compilation message

alternating.cpp: In member function 'void Seg::update(int, int, int, int, int, int)':
alternating.cpp:34:19: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   34 |         int m = s + e >> 1;
      |                 ~~^~~
alternating.cpp: In member function 'int Seg::query(int, int, int, int, int)':
alternating.cpp:43:19: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   43 |         int m = s + e >> 1;
      |                 ~~^~~
alternating.cpp: In function 'void even()':
alternating.cpp:90:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<Info>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   90 |     for(int i=0; i<v.size(); i++) a[v[i].x].color = i % 2;
      |                  ~^~~~~~~~~
alternating.cpp: In function 'void odd()':
alternating.cpp:104:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<Info>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  104 |     for(int i=0; i<v.size(); i++) a[v[i].x].color = i % 2;
      |                  ~^~~~~~~~~
alternating.cpp:111:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<Info>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  111 |     for(int i=0; i<v.size(); i++){
      |                  ~^~~~~~~~~

Subtask #1
0 / 13.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 9196 KB Output is correct
2 Correct 6 ms 9216 KB Output is correct
3 Correct 7 ms 9196 KB Output is correct
4 Correct 6 ms 9216 KB Output is correct
5 Correct 6 ms 9196 KB Output is correct
6 Correct 6 ms 9196 KB Output is correct
7 Correct 6 ms 9196 KB Output is correct
8 Correct 6 ms 9196 KB Output is correct
9 Correct 6 ms 9196 KB Output is correct
10 Correct 6 ms 9216 KB Output is correct
11 Correct 6 ms 9196 KB Output is correct
12 Incorrect 6 ms 9196 KB 'impossible' claimed, but there is a solution
13 Halted 0 ms 0 KB -

Subtask #2
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 9196 KB Output is correct
2 Correct 6 ms 9216 KB Output is correct
3 Correct 7 ms 9196 KB Output is correct
4 Correct 6 ms 9216 KB Output is correct
5 Correct 6 ms 9196 KB Output is correct
6 Correct 6 ms 9196 KB Output is correct
7 Correct 6 ms 9196 KB Output is correct
8 Correct 6 ms 9196 KB Output is correct
9 Correct 6 ms 9196 KB Output is correct
10 Correct 6 ms 9216 KB Output is correct
11 Correct 6 ms 9196 KB Output is correct
12 Incorrect 6 ms 9196 KB 'impossible' claimed, but there is a solution
13 Halted 0 ms 0 KB -

Subtask #3
0 / 22.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 9196 KB Output is correct
2 Correct 6 ms 9216 KB Output is correct
3 Correct 7 ms 9196 KB Output is correct
4 Correct 6 ms 9216 KB Output is correct
5 Correct 6 ms 9196 KB Output is correct
6 Correct 6 ms 9196 KB Output is correct
7 Correct 6 ms 9196 KB Output is correct
8 Correct 6 ms 9196 KB Output is correct
9 Correct 6 ms 9196 KB Output is correct
10 Correct 6 ms 9216 KB Output is correct
11 Correct 6 ms 9196 KB Output is correct
12 Incorrect 6 ms 9196 KB 'impossible' claimed, but there is a solution
13 Halted 0 ms 0 KB -

Subtask #4
0 / 19.0

# Verdict Execution time Memory Grader output
1 Correct 47 ms 16484 KB Output is correct
2 Correct 6 ms 9196 KB Output is correct
3 Correct 102 ms 9584 KB Output is correct
4 Correct 47 ms 9584 KB Output is correct
5 Correct 98 ms 13824 KB Output is correct
6 Correct 169 ms 12028 KB Output is correct
7 Correct 85 ms 10972 KB Output is correct
8 Correct 9 ms 9324 KB Output is correct
9 Correct 7 ms 9196 KB Output is correct
10 Correct 107 ms 14028 KB Output is correct
11 Correct 77 ms 11616 KB Output is correct
12 Correct 75 ms 9868 KB Output is correct
13 Correct 6 ms 9196 KB Output is correct
14 Correct 6 ms 9196 KB Output is correct
15 Incorrect 78 ms 9704 KB 'impossible' claimed, but there is a solution
16 Halted 0 ms 0 KB -

Subtask #5
0 / 26.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 9196 KB Output is correct
2 Correct 6 ms 9216 KB Output is correct
3 Correct 7 ms 9196 KB Output is correct
4 Correct 6 ms 9216 KB Output is correct
5 Correct 6 ms 9196 KB Output is correct
6 Correct 6 ms 9196 KB Output is correct
7 Correct 6 ms 9196 KB Output is correct
8 Correct 6 ms 9196 KB Output is correct
9 Correct 6 ms 9196 KB Output is correct
10 Correct 6 ms 9216 KB Output is correct
11 Correct 6 ms 9196 KB Output is correct
12 Incorrect 6 ms 9196 KB 'impossible' claimed, but there is a solution
13 Halted 0 ms 0 KB -