HDU 1003 Max Sum

分治写法。

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<iostream>
using namespace std;
typedef long long LL;
const double pi=acos(-1.0),eps=1e-8;
void File()
{
    freopen("D:\\in.txt","r",stdin);
    freopen("D:\\out.txt","w",stdout);
}
inline int read()
{
    char c = getchar();  while(!isdigit(c)) c = getchar();
    int x = 0;
    while(isdigit(c)) { x = x * 10 + c - '0'; c = getchar(); }
    return x;
}

const int maxn=100010;
int T,n,a[maxn],L,R,ans;

void check(int l,int r,int s)
{
    if(s<ans) return;
    if(s>ans) { L=l, R=r, ans=s; return ;}
    if(l<L) L=l, R=r, ans=s;
    else if(l==L&&r<R) L=l, R=r, ans=s;
}

int get(int l,int r)
{
    if(l==r) { check(l,r,a[l]); return a[l]; }
    
    int m=(l+r)/2; int x1=get(l,m),x2=get(m+1,r);
    
    int sum1=0,f1=-2000,posl;
    for(int i=m;i>=l;i--) sum1=sum1+a[i],f1=max(f1,sum1);
    sum1=0; for(int i=m;i>=l;i--) { sum1=sum1+a[i]; if(sum1==f1) posl=i; }
    
    int sum2=0,f2=-2000,posr;
    for(int i=m+1;i<=r;i++) sum2=sum2+a[i],f2=max(f2,sum2);
    sum2=0; for(int i=m+1;i<=r;i++) { sum2=sum2+a[i]; if(sum2==f2) {posr=i;break;} }
    
    check(posl,posr,f1+f2);
    
    return max(x1,max(x2,f1+f2));
}

int main()
{
    scanf("%d",&T); int cas=1;
    while(T--)
    {
        scanf("%d",&n); for(int i=1;i<=n;i++) scanf("%d",&a[i]);
        ans=-2000,L=n+1,R=n+1;
        get(1,n); printf("Case %d:\n",cas++);
        printf("%d %d %d\n",ans,L,R);
        if(T) printf("\n");
    }
    return 0;
}