52 lines
1.1 KiB
C++
52 lines
1.1 KiB
C++
#include<cstdio>
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#include<cstring>
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#include<algorithm>
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using namespace std;
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const int maxn=1000005;
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const int P=13141;
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char s[maxn],rs[maxn];
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int n,kase;
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unsigned long long H[maxn],RH[maxn],pm[maxn];
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int solve()
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{
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n=strlen(s+1);
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memcpy(rs,s,n+1);
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reverse(rs+1,rs+1+n);
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for(int i=1;i<=n;i++) H[i]=H[i-1]*P+(s[i]-'a'+1);
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for(int i=1;i<=n;i++) RH[i]=RH[i-1]*P+(rs[i]-'a'+1);
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int res=0;
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for(int i=1,ri=n;i<=n;i++,ri--) // 长度为奇数,以s[i]为中心
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{
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int L=0,R=min(i-1,n-i),M,now=0;
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while(L<=R)
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{
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M=(L+R)>>1;
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if(H[i-1]-H[i-1-M]*pm[M]==RH[ri-1]-RH[ri-1-M]*pm[M]) L=M+1,now=M;
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else R=M-1;
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}
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res=max(res,now*2+1);
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}
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for(int i=2,ri=n-1;i<=n;i++,ri--) // 长度为偶数,以s[i-1]和s[i]为中心
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{
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int L=0,R=min(i-1,n-i+1),M,now=0;
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while(L<=R)
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{
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M=(L+R)>>1;
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if(H[i-1]-H[i-1-M]*pm[M]==RH[ri]-RH[ri-M]*pm[M]) L=M+1,now=M;
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else R=M-1;
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}
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res=max(res,now*2);
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}
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return res;
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}
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int main()
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{
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#ifdef local
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freopen("pro.in","r",stdin);
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#endif
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pm[0]=1;
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for(int i=1;i<=1000000;i++) pm[i]=pm[i-1]*P;
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while(scanf("%s",s+1),strcmp(s+1,"END")) printf("Case %d: %d\n",++kase,solve());
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return 0;
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}
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