Submission #884865

#	Time	Username	Problem	Language	Result	Execution time	Memory
884865		vjudge1	Split the sequence (APIO14_sequence)	C++17	100 / 100	1058 ms	83500 KiB

sequence

#include <bits/stdc++.h>

#define fi first
#define se second

const int N = 1e5 + 5;
const int K = 205;
const int mod = 1e9 + 7;
const int inf = 1e18 + 7;

#define all(v) (v).begin(), (v).end()
#define pii pair<long long, int> 

using namespace std;

mt19937 rd(chrono::steady_clock::now().time_since_epoch().count());

int n, k, trace[K][N], a[N];
long long dp[2][N], f[N];

long long cost(int i, int j){
	return (f[n] - f[j]) * (f[j] - f[i - 1]);
}

void solve(int l, int r, int u, int v, int j){
	if(l > r) return;
	int mid = l + r >> 1;
	pii best = {-inf, -1};
	for(int pos = u; pos <= min(mid, v); pos++){
		best = max(best, {dp[j & 1 ^ 1][pos - 1] + cost(pos, mid), pos});
	}
	dp[j & 1][mid] = best.fi;
	trace[j][mid] = best.se;
	if(best.se == -1) return;
	solve(l, mid - 1, u, best.se, j);
	solve(mid + 1, r, best.se, v, j);
}

signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    
    if(ifstream("sequence.in")){
    	freopen("sequence.in", "r", stdin);
    	freopen("sequence.out", "w", stdout);
    }
    
    cin >> n >> k;
    for(int i = 1; i <= n; i++){
    	cin >> a[i];
    	f[i] = f[i - 1] + a[i];
    	dp[0][i] = -inf;
    }
    for(int j = 1; j <= k; j++){
    	for(int i = 0; i <= n; i++) dp[j & 1][i] = -inf;
    	solve(1, n - 1, 1, n - 1, j);
    }
    long long res = -1;
    int pos = -1;
    for(int i = 1; i < n; i++){
    	if(dp[k & 1][i] > res){
    		res = dp[k & 1][i];
    		pos = i;
    	}
    }
    cout << res << '\n';
    stack<int> split;
    for(; k; k--){
    	split.push(pos);
    	pos = trace[k][pos] - 1;
    }
    while(split.size()){
    	cout << split.top() << ' ';
    	split.pop();
    }
    
    return 0;
}

// tuntun

Compilation message (stderr)

sequence.cpp:9:22: warning: overflow in conversion from 'double' to 'int' changes value from '1.0e+18' to '2147483647' [-Woverflow]
    9 | const int inf = 1e18 + 7;
      |                 ~~~~~^~~
sequence.cpp: In function 'void solve(int, int, int, int, int)':
sequence.cpp:27:14: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   27 |  int mid = l + r >> 1;
      |            ~~^~~
sequence.cpp:30:26: warning: suggest parentheses around arithmetic in operand of '^' [-Wparentheses]
   30 |   best = max(best, {dp[j & 1 ^ 1][pos - 1] + cost(pos, mid), pos});
      |                        ~~^~~
sequence.cpp: In function 'int main()':
sequence.cpp:44:13: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   44 |      freopen("sequence.in", "r", stdin);
      |      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
sequence.cpp:45:13: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   45 |      freopen("sequence.out", "w", stdout);
      |      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 11 / 11
• Subtask 3: 11 / 11
• Subtask 4: 17 / 17
• Subtask 5: 21 / 21
• Subtask 6: 29 / 29