UVALive - 8086 Substring Sorting (后缀数组+线段树上二分)

#include<bits/stdc++.h>

#define rep(i,e) for(int i=0;i<(e);i++)
#define rep1(i,e) for(int i=1;i<=(e);i++)
#define repx(i,x,e) for(int i=(x);i<=(e);i++)
#define pii pair<int,int>
#define X first
#define Y second
#define PB push_back
#define MP make_pair
#define mset(var,val) memset(var,val,sizeof(var))
#define scd(a) scanf("%d",&a)
#define scdd(a,b) scanf("%d%d",&a,&b)
#define scddd(a,b,c) scanf("%d%d%d",&a,&b,&c)
#define IOS ios::sync_with_stdio(false);cin.tie(0)

using namespace std;

typedef long long ll;
template <class T>
void test(T a){cout<<a<<endl;}
template <class T,class T2>
void test(T a,T2 b){cout<<a<<" "<<b<<endl;}
template <class T,class T2,class T3>
void test(T a,T2 b,T3 c){cout<<a<<" "<<b<<" "<<c<<endl;}
const int N = 2e6+10;
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9+7;
struct Node{
    int lc,rc;
    int val;
    void init(){
        lc=rc=val=0;
    }
}tree[N];
int tot;
void init(){
    tot=1;
    tree[0].init();
}
int update(int i, int l,int r,int pos){
    //原本想用区间第k大解决，发现做不了...
    //所以这个线段树是可持续化的写法（其实只是懒得改）
    int rt = tot++;
    tree[rt].init();
    tree[rt].val = 1;
    if(l==r){
        return rt;
    }
    int mid = l+r>>1;
    if(pos<=mid){
        tree[rt].rc = tree[i].rc;
        tree[rt].lc = update(tree[i].lc, l,mid,pos);
    }else {
        tree[rt].lc = tree[i].lc;
        tree[rt].rc = update(tree[i].rc, mid+1,r,pos);
    }
    tree[rt].val = tree[tree[rt].lc].val + tree[tree[rt].rc].val;
    return rt;
}
void del(int i,int l,int r,int pos){
    tree[i].val = 0;
    if(l==r){
        return;
    }
    int mid = l+r>>1;
    if(pos<=mid) del(tree[i].lc, l,mid,pos);
    else del(tree[i].rc,mid+1,r,pos);
    tree[i].val = tree[tree[i].lc].val + tree[tree[i].rc].val;
}
int n;

int query(int i,int l,int r, int k){
    if(tree[i].val < k) return -1;
    if(l==r) return l;
    int mid = l+r>>1;
    int lc = tree[i].lc;
    if(tree[lc].val >= k){
        return query(lc, l,mid,k);
    }else return query(tree[i].rc, mid+1, r, k-tree[lc].val);
}

int rnk[N],sa[N], height[N], tmp[N], cnt[N];char s[N];
void suf(int n,int m){
    int i,j,k;
    n++;
    for(i=0;i<n*2+5;i++)rnk[i]=sa[i]=height[i]=tmp[i]=0;
    for(i=0;i<m;i++)cnt[i]=0;
    for(i=0;i<n;i++)cnt[rnk[i]=s[i]]++;
    for(i=1;i<m;i++)cnt[i]+=cnt[i-1];
    for(i=0;i<n;i++)sa[--cnt[rnk[i]]] = i;
    for(int k = 1;k<=n;k<<=1){
        for(i=0;i<n;i++){
            int j = sa[i]-k;
            if(j<0) j+=n;
            tmp[cnt[rnk[j]]++]=j;
        }
        sa[tmp[cnt[0]=0]]=j=0;
        for(i=1;i<n;i++){
            if(rnk[tmp[i]]!=rnk[tmp[i-1]] || rnk[tmp[i]+k]!=rnk[tmp[i-1]+k])cnt[++j]=i;
            sa[tmp[i]] = j;
        }
        memcpy(rnk, sa, n*sizeof(int));
        memcpy(sa, tmp, n*sizeof(int));
        if(j>=n-1) break;
    }
    for(j = rnk[height[i=k=0]=0];i<n-1;i++,k++){
        while(~k&&s[i]!=s[sa[j-1]+k]) height[j]=k--,j=rnk[sa[j]+1];
    }
}
struct Query{
    int len,k,i;
    bool operator < (const Query &b)const{
        return len<b.len;
    }
}p[N];
pii pos[N];
int ans[N];
int mi[2][N][20];
void rmqinit(){
    rep1(i,n){
        mi[0][i][0] = height[i];
        mi[1][i][0] = sa[i];
    }
    rep(d,2)
    for(int k = 1;(1<<k)<=n;k++){
        for(int i = 1;i+(1<<k)-1<=n;i++){
            mi[d][i][k] = min(mi[d][i][k-1], mi[d][i+(1<<k-1)][k-1]);
        }
    }
}
int rmqquery(int l,int r,int d){
    int k = log2(r-l+1);
    return min(mi[d][l][k], mi[d][r-(1<<k)+1][k]);
}
int rmqquery(int x, int len){
    int A = x+1, B = n;
    int r=x;
    while(A<=B){
        int mid = A+B>>1;
        if(rmqquery(x+1,mid,0) >= len){
            r = mid;
            A = mid+1;
        }else B = mid-1;
    }
    int l = x;
    return rmqquery(l,r,1);
}

void work(){
    init();
    scanf("%s",s);
    n = strlen(s);
    suf(n,128);
    int q;scd(q);
    rep(i,q){
        int len,k;scdd(len,k);
        p[i].i = i;
        p[i].len = len;
        p[i].k = k;
    }
    sort(p,p+q);
    rep1(i,n){
        pos[i] = MP(height[i], i);
    }
    sort(pos+1,pos+1+n);
    int idx = 1;
    int rt = 0;
    rmqinit();
    priority_queue<int> que;
    for(int i = 0;i<q;){
        int len = p[i].len;
        while(idx<=n && pos[idx].X < len){
            int r = pos[idx].Y;
            rt = update(rt, 0,n,r);
            que.push(sa[r]);
            idx++;
        }
        while(!que.empty() && n - que.top() < len){
            int top = que.top();que.pop();
            del(rt, 0, n, rnk[top]);
        }
        while(i<q && p[i].len == len){
            int r = query(rt, 0,n,p[i].k);
            if(r==-1) ans[p[i].i] = -1;
            else {
                ans[p[i].i] = rmqquery(r, len);
            }
            i++;
        }
    }
    rep(i,q){
        if(ans[i]==-1){
            puts("Not found");
        }else printf("%d\n", ans[i]);
    }
}
int main() {
    #ifdef local
    freopen("in.txt","r",stdin);
    #endif // local
//    IOS;
    int t;scd(t);while(t--)
        work();
}