101 to 010 Atcoder CODE FESTIVAL 2017 qual B D

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https://www.luogu.org/problemnew/show/AT3575

題解

根本不會。。

錯誤記錄：缺少32行的轉移。顯然這個轉移是必要的

 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_back10 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 }

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101 to 010 Atcoder CODE FESTIVAL 2017 qual B D