Submission #382281

#TimeUsernameProblemLanguageResultExecution timeMemory
382281couplefireBuilding 4 (JOI20_building4)C++17
100 / 100
348 ms74472 KiB
#include <bits/stdc++.h> using namespace std; #define MAXN 500005 int n; int arr[2*MAXN], brr[2*MAXN]; array<int, 2> dp[2*MAXN][2]; //a = 0, b = 1 vector<char> ans; array<int, 2> comb(array<int, 2> a, array<int, 2> b){ if(a[0] == -1) return b; if(b[0] == -1) return a; return {min(a[0], b[0]), max(a[1], b[1])}; } array<int, 2> add1(array<int, 2> a){ if(a[0] == -1) return a; return {a[0]+1, a[1]+1}; } bool contain(array<int, 2> a, int val){ return val >= a[0] && a[1] >= val; } void trace(int i, int j, int val){ if(i == 0){ if(j == 0) ans.push_back('A'); else ans.push_back('B'); return; } if(j == 0){ if(arr[i] >= arr[i-1]){ if(contain(dp[i-1][0], val)){ ans.push_back('A'); trace(i-1, 0, val); return; } } if(arr[i] >= brr[i-1]){ if(contain(dp[i-1][1], val)){ ans.push_back('A'); trace(i-1, 1, val); return; } } } else{ if(brr[i] >= arr[i-1]){ if(contain(add1(dp[i-1][0]), val)){ ans.push_back('B'); trace(i-1, 0, val-1); return; } } if(brr[i] >= brr[i-1]){ if(contain(add1(dp[i-1][1]), val)){ ans.push_back('B'); trace(i-1, 1, val-1); return; } } } } int main(){ // freopen("a.in", "r", stdin); ios_base::sync_with_stdio(false); cin.tie(0); cin >> n; for(int i = 0; i<2*n; i++) cin >> arr[i]; for(int i = 0; i<2*n; i++) cin >> brr[i]; for(int i = 0; i<2*n; i++) dp[i][0] = dp[i][1] = {-1, -1}; dp[0][0] = {0, 0}; dp[0][1] = {1, 1}; for(int i = 1; i<2*n; i++){ if(arr[i] >= arr[i-1]) dp[i][0] = comb(dp[i][0], dp[i-1][0]); if(arr[i] >= brr[i-1]) dp[i][0] = comb(dp[i][0], dp[i-1][1]); if(brr[i] >= arr[i-1]) dp[i][1] = comb(dp[i][1], add1(dp[i-1][0])); if(brr[i] >= brr[i-1]) dp[i][1] = comb(dp[i][1], add1(dp[i-1][1])); } if(!(contain(dp[2*n-1][0], n) || contain(dp[2*n-1][1], n))){ cout << -1 << endl; return 0; } if(contain(dp[2*n-1][0], n)) trace(2*n-1, 0, n); else trace(2*n-1, 1, n); reverse(ans.begin(), ans.end()); for(auto x : ans) cout << x; cout << endl; }
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