实验基地(base)

xiaoxiao2021-02-28  7

http://120.78.128.11/Problem.jsp?pid=3091

中文题就不讲题意了。

做法:维护第一行的i-j的最小值,也就是凹进去的那一部分。

预处理,然后处理一个前缀和,n^2的代价维护i-j的总值,然

后再减去中间的最小值。

/// .-~~~~~~~~~-._ _.-~~~~~~~~~-. /// __.' ~. .~ `.__ /// .'// \./ \\`. /// .'// | \\`. /// .'// .-~"""""""~~~~-._ | _,-~~~~"""""""~-. \\`. /// .'//.-" `-. | .-' "-.\\`. /// .'//______.============-.. \ | / ..-============.______\\`. /// .'______________________________\|/______________________________`. #pragma comment(linker, "/STACK:1024000000,1024000000") #include <vector> #include <iostream> #include <string> #include <map> #include <stack> #include <cstring> #include <queue> #include <list> #include <stdio.h> #include <set> #include <algorithm> #include <cstdlib> #include <cmath> #include <iomanip> #include <cctype> #include <sstream> #include <functional> #include <stdlib.h> #include <time.h> #include <bitset> using namespace std; #define pi acos(-1) #define s_1(x) scanf("%d",&x) #define s_2(x,y) scanf("%d%d",&x,&y) #define s_3(x,y,z) scanf("%d%d%d",&x,&y,&z) #define s_4(x,y,z,X) scanf("%d%d%d%d",&x,&y,&z,&X) #define S_1(x) scan_d(x) #define S_2(x,y) scan_d(x),scan_d(y) #define S_3(x,y,z) scan_d(x),scan_d(y),scan_d(z) #define PI acos(-1) #define endl '\n' #define srand() srand(time(0)); #define me(x,y) memset(x,y,sizeof(x)); #define foreach(it,a) for(__typeof((a).begin()) it=(a).begin();it!=(a).end();it++) #define close() ios::sync_with_stdio(0); cin.tie(0); #define FOR(x,n,i) for(int i=x;i<=n;i++) #define FOr(x,n,i) for(int i=x;i<n;i++) #define fOR(n,x,i) for(int i=n;i>=x;i--) #define fOr(n,x,i) for(int i=n;i>x;i--) #define W while #define sgn(x) ((x) < 0 ? -1 : (x) > 0) #define bug printf("***********\n"); #define db double #define ll long long #define mp make_pair #define pb push_back typedef long long LL; typedef pair <int, int> ii; const int INF=0x3f3f3f3f; const LL LINF=0x3f3f3f3f3f3f3f3fLL; const int dx[]={-1,0,1,0,1,-1,-1,1}; const int dy[]={0,1,0,-1,-1,1,-1,1}; const int maxn=2e3+10; const int maxx=1e3+10; const double EPS=1e-8; const double eps=1e-8; const int mod=1e9+7; template<class T>inline T min(T a,T b,T c) { return min(min(a,b),c);} template<class T>inline T max(T a,T b,T c) { return max(max(a,b),c);} template<class T>inline T min(T a,T b,T c,T d) { return min(min(a,b),min(c,d));} template<class T>inline T max(T a,T b,T c,T d) { return max(max(a,b),max(c,d));} template <class T> inline bool scan_d(T &ret){char c;int sgn;if (c = getchar(), c == EOF){return 0;} while (c != '-' && (c < '0' || c > '9')){c = getchar();}sgn = (c == '-') ? -1 : 1;ret = (c == '-') ? 0 : (c - '0'); while (c = getchar(), c >= '0' && c <= '9'){ret = ret * 10 + (c - '0');}ret *= sgn;return 1;} inline bool scan_lf(double &num){char in;double Dec=0.1;bool IsN=false,IsD=false;in=getchar();if(in==EOF) return false; while(in!='-'&&in!='.'&&(in<'0'||in>'9'))in=getchar();if(in=='-'){IsN=true;num=0;}else if(in=='.'){IsD=true;num=0;} else num=in-'0';if(!IsD){while(in=getchar(),in>='0'&&in<='9'){num*=10;num+=in-'0';}} if(in!='.'){if(IsN) num=-num;return true;}else{while(in=getchar(),in>='0'&&in<='9'){num+=Dec*(in-'0');Dec*=0.1;}} if(IsN) num=-num;return true;} void Out(LL a){if(a < 0) { putchar('-'); a = -a; }if(a >= 10) Out(a / 10);putchar(a % 10 + '0');} void print(LL a){ Out(a),puts("");} //freopen( "in.txt" , "r" , stdin ); //freopen( "data.txt" , "w" , stdout ); //cerr << "run time is " << clock() << endl; int n; int a[maxn]; LL sum[maxn][maxn]; LL pre[maxn]; LL mic[maxn][maxn]; void solve() { W(cin>>n) { me(mic,0); me(sum,0); FOR(1,n,i) s_1(a[i]); FOR(1,n,i) mic[i][i]=a[i]; FOR(1,n,i) { int mx=a[i],sum=a[i]; FOR(i+1,n,j) { if(sum>0) sum=0; sum+=a[j]; if(sum<mx) mx=sum; mic[i][j]=mx; } } FOR(1,n,i) { int x; s_1(x); a[i]+=x; } pre[0]=0; FOR(1,n,i) pre[i]=pre[i-1]+a[i]; FOR(1,n,i) FOR(i,n,j) sum[i][j]=pre[j]-pre[i-1]; LL ans=-LINF; FOR(1,n,i) { FOR(i+2,n,j) { ans=max(ans,sum[i][j]-mic[i+1][j-1]); } } print(ans); } } int main() { // freopen( "in.txt" , "r" , stdin ); //freopen( "data.txt" , "w" , stdout ); int t=1; //init(); //s_1(t); for(int cas=1;cas<=t;cas++) { //printf("Case #%d: ",cas); solve(); } }

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