101 to 010 Atcoder CODE FESTIVAL 2017 qual B D
https://www.luogu.org/problemnew/show/AT3575
根本不会。。
错误记录：缺少32行的转移。显然这个转移是必要的
1 #include<cstdio> 2 #include<algorithm> 3 #include<cstring> 4 #include<vector> 5 using namespace std; 6 #define fi first 7 #define se second 8 #define mp make_pair 9 #define pb push_back 10 typedef long long ll; 11 typedef unsigned long long ull; 12 typedef pair<int,int> pii; 13 14 int a[500010],ans[500010],pre[500010]; 15 int n; 16 int main() 17 { 18 int i; 19 scanf("%d",&n); 20 for(i=1;i<=n;++i) 21 scanf("%1d",&a[i]); 22 for(i=1;i<=n;++i) 23 pre[i]=a[i]==0?i:pre[i-1]; 24 int pre2=0; 25 for(i=1;i<=n;++i) 26 { 27 if(i>=3&&a[i]==1&&a[i-1]==0&&a[i-2]==1) pre2=i; 28 ans[i]=ans[i-1]; 29 if(i>=3&&a[i-2]==1&&a[i-1]==0&&a[i]==1) 30 { 31 ans[i]=max(ans[i],ans[pre[i-2]]+(i-2-pre[i-2])); 32 ans[i]=max(ans[i],ans[pre[i-2]+1]+(i-2-(pre[i-2]+1))); 33 } 34 if(pre2>pre[i]) 35 { 36 ans[i]=max(ans[i],ans[pre2-3]+(i-pre2+1)); 37 } 38 //printf("1t%d %d\n",i,ans[i]); 39 } 40 printf("%d",ans[n]); 41 return 0; 42 }
