POJ 3261(后缀数组)

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题意：寻找出现至少K次的最长子串
解法：后缀数组裸题
#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>#include <cmath>#include <vector>#include <queue>#include <stack>#include <set>#include <map>#include <queue>//#include <tr1/unordered_set>//#include <tr1/unordered_map>#include <bitset>//#pragma comment(linker, "/STACK:1024000000,1024000000")using namespace std;#define lson l, m, rt<<1#define rson m+1, r, rt<<1|1#define inf 1e9#define debug(a) cout << #a" = " << (a) << endl;#define debugarry(a, n) for (int i = 0; i < (n); i++) { cout << #a"[" << i << "] = " << (a)[i] << endl; }#define clr(x, y) memset(x, y, sizeof x)#define ll long long#define ull unsigned long long#define FOR(i,a,b) \    for(i=a;a<b?i<=b:i>=b;a<b?i++:i--)const int maxn = 20000*2+100;struct suffix_array{    int s[maxn];    int sa[maxn],t[maxn],t2[maxn],c[maxn];    int n;    void build_sa(int m)    {        int i,*x=t,*y=t2;        FOR(i,0,m-1) c[i]=0;        FOR(i,0,n-1) c[x[i]=s[i]]++;        FOR(i,1,m-1) c[i]+=c[i-1];        FOR(i,n-1,0) sa[--c[x[i]]]=i;        for(int k=1;k<=n;k<<=1){            int p=0;            FOR(i,n-k,n-1) y[p++]=i;            FOR(i,0,n-1) if(sa[i]>=k) y[p++]=sa[i]-k;            FOR(i,0,m-1) c[i]=0;            FOR(i,0,n-1) c[x[y[i]]]++;            FOR(i,0,m-1) c[i]+=c[i-1];            FOR(i,n-1,0) sa[--c[x[y[i]]]]=y[i];            swap(x,y);            p=1;            x[sa[0]]=0;            FOR(i,1,n-1)                x[sa[i]]=y[sa[i-1]]==y[sa[i]]&&                y[sa[i-1]+k]==y[sa[i]+k]?p-1:p++;            if(p>=n) break;            m=p;        }    }    int Rank[maxn],height[maxn];    void getHeight()    {        int k=0;        for(int i=0;i<n;i++) Rank[sa[i]]=i;        for(int i=0;i<n;i++){            if(k)k--;            int j=sa[Rank[i]-1];            while(s[i+k]==s[j+k]) k++;            height[Rank[i]]=k;        }    }}su;int num[maxn],sub[maxn],len,n,k;bool cal(int len){    for(int i=1;i<=n;i++)    {        int j;        for(j=i;j<=n&&su.height[j]>=len;j++)            ;        if( j - i >= k - 1 ) return true;    }    return false;}int main(){    //freopen("input.txt","r",stdin);    //  freopen("output.txt","w",stdout);    while(~scanf("%d%d",&n,&k))    {        len=0;        for(int i=0;i<n;i++)        {            scanf("%d",&num[i]);            sub[len++]=num[i];        }        sort(sub,sub+len);        len=unique(sub,sub+len)-sub;        for(int i=0;i<n;i++)            su.s[i] = lower_bound(sub,sub+len,num[i])-sub+1;        su.n = n + 1;        su.build_sa(len+5);        su.getHeight();        int l=1,r=n,ans=1;        while(l<=r)        {            int m=l+r>>1;            if(cal(m))            {                ans=max(ans,m);                l=m+1;            }            else r=m-1;        }        printf("%d\n",ans);    }    return 0;}
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