Submission #833265

#	Time	Username	Problem	Language	Result	Execution time	Memory
833265		josanneo22	Feast (NOI19_feast)	C++17	71 / 100	205 ms	262144 KiB

feast

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ld long double
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define ar array
const int inf=1e15;
long long maxSubArraySum(vector<long long> &a, int size)
{
	long long max_so_far = LLONG_MIN, max_ending_here = 0;
	int starting_index = 0, ending_index = 0, s = 0;
	for (int i = 0; i < size; i++) {
		max_ending_here = max_ending_here + a[i];
		if (max_so_far < max_ending_here) {
			max_so_far = max_ending_here; 
			starting_index = s; 
			ending_index = i;
		}
		if (max_ending_here < 0) {
			max_ending_here = 0;
			s = i + 1;
		}
	}
	return max_so_far;
}
void solve(){
	int n,k; cin>>n>>k;
	vector<int> a(n+1); for(int i=1;i<=n;i++) cin>>a[i];
	if(*min_element(a.begin(), a.end())>=0){
		cout<< accumulate(a.begin(),a.end(),0LL)<<'\n';
		return;
	}
	if(k==1){
		cout<<max(0LL,maxSubArraySum(a,n+1))<<'\n';
		return;
	}
	int cnt=0,pos=-1;
	for(int i=1;i<=n;i++){
		if(a[i]<0){
			cnt++;
			pos=i;
		}
	}
	if(cnt<=1){
		int ans=max(0LL,accumulate(a.begin(),a.end(),0LL));
		if(pos==-1){ cout<<ans<<'\n'; return;}
		else{
			int S1=0,S2=0;
			for(int i=1;i<pos;i++) S1+=a[i];
			for(int i=pos+1;i<=n;i++) S2+=a[i];
			cout<<S1+S2<<'\n';
			return;
		}
	}
	vector<vector<vector<int>>> dp(n+1,vector<vector<int>>(n+1,vector<int>(2,-inf)));
	dp[0][0][0]=0; dp[0][0][1]=0; int ans=0;
	for(int i=1;i<=n;i++){
		dp[i][0][0]=0;
		for(int j=1;j<=n;j++){
			dp[i][j][0]=max(dp[i-1][j][0],dp[i-1][j][1]);
			dp[i][j][1]=max(dp[i-1][j][1],dp[i-1][j-1][0])+a[i];
			if(j<=k) ans=max(ans,max(dp[i][j][0],dp[i][j][1]));
		}
	}
	cout<<ans<<'\n';
}

signed main() {
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	clock_t tStart = clock();
	int local=0,multi=0,debug=1,tt=1;
	if(local){
	    freopen("input.txt","r",stdin);
	    freopen("output.txt","w",stdout);
	}	
	if(multi) cin>>tt;
	for(int i=1;i<=tt;i++){
		if(debug && multi && local) cout<<"样例 "<<i<<'\n';
		solve();
 	}
	fprintf(stderr, "\n>> Runtime: %.10fs\n", (double) (clock() - tStart) / CLOCKS_PER_SEC);
}

Compilation message (stderr)

feast.cpp: In function 'long long int maxSubArraySum(std::vector<long long int>&, long long int)':
feast.cpp:16:6: warning: variable 'starting_index' set but not used [-Wunused-but-set-variable]
   16 |  int starting_index = 0, ending_index = 0, s = 0;
      |      ^~~~~~~~~~~~~~
feast.cpp:16:26: warning: variable 'ending_index' set but not used [-Wunused-but-set-variable]
   16 |  int starting_index = 0, ending_index = 0, s = 0;
      |                          ^~~~~~~~~~~~
feast.cpp: In function 'int main()':
feast.cpp:78:13: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   78 |      freopen("input.txt","r",stdin);
      |      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
feast.cpp:79:13: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   79 |      freopen("output.txt","w",stdout);
      |      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 8 / 8
• Subtask 3: 18 / 18
• Subtask 4: 10 / 10
• Subtask 5: 11 / 11
• Subtask 6: 20 / 20
• Subtask 7: 0 / 29