hdu 4080 Stammering Aliens 二分 hash

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POJ 3882 TLE 需后缀数组

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const int SEED = 13331;const int MAX_N = 50000 + 10;char s[MAX_N];struct HASH{    ULL H[MAX_N];    ULL XL[MAX_N];    int len;    HASH(){}    void build(char *s){        len=strlen(s);        H[len]=0;        XL[0]=1;        for (int i=len-1;i>=0;i--){            H[i]=H[i+1]*SEED+s[i];            XL[len-i]=XL[len-i-1]*SEED;        }    }    ULL hash(int i,int L){        return H[i]-H[i+L]*XL[L];    }}hs;int n,m;ULL a[MAX_N];int id[MAX_N];int idx;bool cmp(int x,int y){    if (a[x]==a[y]) return x<y;    return a[x]<a[y];}bool C(int L) {    int cnt=0,sum=1;    idx=-1;    for (int i=0;i+L<=n;i++) {        a[cnt]=hs.hash(i,L);        id[cnt++]=i;    }    sort(id,id+cnt,cmp);    for (int i=1;i<cnt;i++) {        if (a[id[i]]==a[id[i-1]]) {            sum++;            if (sum>=m) idx=max(idx,id[i]);        }        else sum=1;    }    return idx>=0;}int main(){    while (~scanf("%d",&m)) {        if (m==0) break;        scanf("%s",s);        hs.build(s);        n=strlen(s);        if(m==1) {            printf("%d %d\n",n,0);            continue;        }        if(!C(1)) {            printf("none\n");            continue;        }        int l=1,r=n;        int ans=0;        while (l<=r) {            int mid=(l+r)>>1;            if (C(mid)) {                ans=mid;                l=mid+1;            }            else r=mid-1;        }        C(ans);        if (ans==0) printf("none\n");        else printf("%d %d\n",ans,idx);    }return 0;}

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