Submission #229289

#	Time	Username	Problem	Language	Result	Execution time	Memory
229289		xiaowuc1	건물 4 (JOI20_building4)	C++14	100 / 100	350 ms	44272 KiB

building4

#include <algorithm>
#include <bitset>
#include <cassert>
#include <chrono>
#include <complex>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <vector>

using namespace std;

// BEGIN NO SAD
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()
#define derr if(1) cerr
typedef vector<int> vi;
// END NO SAD

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<vector<ll>> matrix;
typedef pair<int, pii> state;

void die() {
  cout << "-1\n";
  exit(0);
}

int a[1000000];
int b[1000000];
pii dp[1000001][2]; // [i][0] gives range of min, max of A's, selecting A last
const pii BAD = {1e9, -1e9};
void solve() {
  int n;
  cin >> n;
  n *= 2;
  int want = n/2;
  for(int i = 0; i < n; i++) cin >> a[i];
  for(int i = 0; i < n; i++) cin >> b[i];
  dp[1][0] = {1, 1};
  dp[1][1] = {0, 0};
  for(int i = 1; i < n; i++) {
    int clhs = 1e9;
    int crhs = -1e9;
    if(a[i] >= a[i-1]) {
      clhs = min(clhs, dp[i][0].first + 1);
      crhs = max(crhs, dp[i][0].second + 1);
    }
    if(a[i] >= b[i-1]) {
      clhs = min(clhs, dp[i][1].first + 1);
      crhs = max(crhs, dp[i][1].second + 1);
    }
    dp[i+1][0] = {clhs, crhs};
    clhs = 1e9;
    crhs = -1e9;
    if(b[i] >= a[i-1]) {
      clhs = min(clhs, dp[i][0].first);
      crhs = max(crhs, dp[i][0].second);
    }
    if(b[i] >= b[i-1]) {
      clhs = min(clhs, dp[i][1].first);
      crhs = max(crhs, dp[i][1].second);
    }
    dp[i+1][1] = {clhs, crhs};
  }
  pii src = {-1, -1};
  if(dp[n][0].first <= want && want <= dp[n][0].second) src = {n, 0};
  if(dp[n][1].first <= want && want <= dp[n][1].second) src = {n, 1};
  if(src.first == -1) die();
  vector<char> ret;
  int numa = want;
  while(src.first) {
    if(src.second) ret.push_back('B');
    else {
      ret.push_back('A');
      numa--;
    }
    if(--src.first == 0) break;
    int now = src.second ? b[src.first] : a[src.first];
    if(now >= a[src.first-1] && dp[src.first][0].first <= numa && numa <= dp[src.first][0].second) {
      src.second = 0;
    }
    else {
      src.second = 1;
    }
    assert(dp[src.first][src.second].first <= numa && numa <= dp[src.first][src.second].second);
  }
  reverse(all(ret));
  for(char out: ret) cout << out; cout << "\n";
}
// are there edge cases (N=1?)
// are array sizes proper (scaled by proper constant, for example 2* for koosaga tree)
// integer overflow?
// DS reset properly between test cases

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL); cout.tie(NULL);
  solve();
}

Compilation message (stderr)

building4.cpp: In function 'void solve()':
building4.cpp:97:3: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
   for(char out: ret) cout << out; cout << "\n";
   ^~~
building4.cpp:97:35: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
   for(char out: ret) cout << out; cout << "\n";
                                   ^~~~

• Subtask 1: 11 / 11
• Subtask 2: 89 / 89