Submission #854875

#	Time	Username	Problem	Language	Result	Execution time	Memory
854875		mychecksedad	Election (BOI18_election)	C++17	82 / 100	110 ms	35816 KiB

election

/* Author : Mychecksdead  */
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define MOD (1000000000+7)
#define MOD1 (998244353)
#define pb push_back
#define all(x) x.begin(), x.end()
#define en cout << '\n'
const int N = 1e6+100, M = 1e5+10, K = 22;

int n, q, go[N][K], dp[N][K][2], a[N];
string s, t;
vector<int> pref;
array<int, 3> T[N];
array<int, 3> combine(array<int, 3> x, array<int, 3> y){
  return {
    min(x[0], x[2] + y[0]),
    min(y[1], x[1] + y[2]),
    x[2] + y[2]
  };
}
 
void build(int l, int r, int k){
  if(l == r){
    T[k][0] = s[l - 1] == 'T' ? -1 : 0;
    T[k][1] = T[k][0];
    T[k][2] = s[l - 1] == 'T' ? -1 : 1;
    return;
  }
  int m = l+r>>1;
  build(l, m, k<<1);
  build(m+1, r, k<<1|1);
  T[k] = combine(T[k<<1], T[k<<1|1]);
}

array<int, 3> get(int l, int r, int ql, int qr, int k){
  if(ql > r || qr < l) return {0, 0, 0};
  if(ql <= l && r <= qr) return T[k];
  int m = l + r >> 1;
  auto x = get(l, m, ql, qr, k<<1);
  auto y = get(m+1, r, ql, qr, k<<1|1);
  return combine(x, y);
}

void solve(){
  cin >> n >> s;
  cin >> q;

  for(int i = 1; i <= n; ++i) a[i] = (s[i - 1] == 'T' ? -1 : 1);

  pref.resize(n + 1);
  
  pref[0] = 0;
  for(int i = 1; i <= n; ++i) pref[i] = pref[i - 1] + a[i];

  build(1, n, 1); 

  map<int, int> last;
  last[0] = n + 1;
  int sum = 0;
  for(int i = n; i >= 1; --i){
    sum += a[i];
    if(a[i] == -1){
      go[i][0] = i + 1;
      dp[i][0][0] = 1;
      dp[i][0][1] = 0;
    }
    else if(last[sum]){
      go[i][0] = last[sum];
      dp[i][0][1] = -get(1, n, i, go[i][0] - 1, 1)[1];
      dp[i][0][0] = 0;
    }else go[i][0] = n + 1, dp[i][0][1] = -get(1, n, i, n, 1)[1], dp[i][0][0] = 0;
    last[sum] = i;
  }
  go[n+1][0] = n+1;
  dp[n + 1][0][0] = 0;
  dp[n + 1][0][1] = 0;
  for(int j = 1; j < K; ++j){
    for(int i= 1; i <= n+1; ++i){
      go[i][j] = go[go[i][j - 1]][j - 1];
      dp[i][j][0] = dp[i][j - 1][0] + dp[go[i][j - 1]][j - 1][0];
      dp[i][j][1] = max(dp[i][j - 1][1], dp[go[i][j - 1]][j - 1][1]);
    }
  }

  for(int i = 0; i < q; ++i){
    int l, r; cin >> l >> r;
    pair<int, int> ans = {0, 0};
    for(int j = K - 1; j >= 0; --j){
      if(go[l][j] <= r){
        ans.first += dp[l][j][0];
        ans.second = max(dp[l][j][1], ans.second);
        l = go[l][j];
      }
    }
    int ss = pref[r] - pref[l - 1];
    ans.second = max(0, ans.second - ss);
    ans.second = max(ans.second, -get(1, n, l, r, 1)[1]);
    cout << ans.first + ans.second << '\n';
  }

}


int main(){
  cin.tie(0); ios::sync_with_stdio(0);
  int tt = 1, aa;
  // freopen("in.txt", "r", stdin);
  // freopen("out.txt", "w", stdout);
  // cin >> tt;
  while(tt--){
    solve();
    // en;
  }
  cerr<<"time taken : "<<(float)clock()/CLOCKS_PER_SEC<<" seconds\n";
  return 0;
} 

Compilation message (stderr)

election.cpp: In function 'void build(int, int, int)':
election.cpp:31:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   31 |   int m = l+r>>1;
      |           ~^~
election.cpp: In function 'std::array<int, 3> get(int, int, int, int, int)':
election.cpp:40:13: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   40 |   int m = l + r >> 1;
      |           ~~^~~
election.cpp: In function 'int main()':
election.cpp:108:15: warning: unused variable 'aa' [-Wunused-variable]
  108 |   int tt = 1, aa;
      |               ^~

• Subtask 1: 28 / 28
• Subtask 2: 54 / 54
• Subtask 3: 0 / 18