hdu 4080 Stammering Aliens 二分 hash

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,0);
            continue;
        }
        if(!C(1)) {
            printf("none
");
            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
");
        else printf("%d %d
",ans,idx);
    }
	return 0;
}

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