Manacher演算法(最長迴文子串)

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#include<cstdio>#include<cstring>#include<algorithm>using namespace std;const int maxn=11000000;char s[maxn+10],a[(maxn<<1)+10]; int l,n,maxv,pos,rl[(maxn<<1)+10],ans;int main(){    scanf("%s",s); l=strlen(s);    for(register int i=0;i<l;++i){a[++n]=s[i]; ++n;}    maxv=pos=0; rl[0]=1;    for(register int i=1;i<=n;++i){        if(i<=maxv) rl[i]=min(rl[(pos<<1)-i],maxv-i);        else rl[i]=1;        for(;i+rl[i]<=n&&i-rl[i]>=0&&a[i-rl[i]]==a[i+rl[i]];++rl[i]);        if(i+rl[i]-1>maxv){            maxv=i+rl[i]-1; pos=i;        }        ans=max(ans,rl[i]-1);    }    printf("%d",ans); return 0;}

 

Manacher演算法(最長迴文子串)