HDU 1003 Maxsum

题目大意：求出数列的最大子段和，并且说明是从第几项至第几项。

题解1：简单贪心。

#include <cstdio> 
#define rep(i,n) for(int i=1;i<=n;i++)
int main(){int t,l=0;scanf("%d",&t);while(t--&&++l){if(l!=1)printf("\n");printf("Case %d:\n",l);int a[100001],f[100001]={0};int max,maxl,maxr,l,r,n;scanf("%d",&n);rep(i,n)scanf("%d",&a[i]);l=1; max=-100000;rep(i,n){if (f[i-1]+a[i]<a[i]){f[i]=a[i];l=i;r=i;}else{f[i]=f[i-1]+a[i];r=i;}if(max<f[i]){max=f[i];maxl=l;maxr=r;} }printf("%d %d %d\n",max,maxl,maxr);}return 0;
}

 题解2：单调队列

#include <cstdio>
using namespace std;
int a[100005],s[100005],num[100005];
int T,n,m,st,ed,h,t,maxs;
int main(){int cnt=0;scanf("%d",&T);while(T--){scanf("%d",&n);int i,j,k; s[0]=0;  for(int i=1;i<=n;i++)scanf("%d",&a[i]),s[i]=s[i-1]+a[i];h=1; t=0; maxs=~0U>>1; maxs=-maxs;for(int i=1;i<=n;i++){while(h<=t&&s[num[t]]>s[i-1])t--;num[++t]=i-1;if(s[i]-s[num[h]]>maxs){maxs=s[i]-s[num[h]];st=num[h]+1; ed=i;}}if(cnt)puts("");printf("Case %d:\n",++cnt);if(st>n)st=st-n; if(ed>n)ed=ed-n;printf("%d %d %d\n",maxs,st,ed);}return 0;
}