hdu 3518 Boring counting 后缀数组

题目链接

根据height数组的性质分组计算。

#include <iostream>
#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <queue>
#include <stack>
#include <bitset>
using namespace std;
#define pb(x) push_back(x)
#define ll long long
#define mk(x, y) make_pair(x, y)
#define lson l, m, rt<<1
#define mem(a) memset(a, 0, sizeof(a))
#define rson m+1, r, rt<<1|1
#define mem1(a) memset(a, -1, sizeof(a))
#define mem2(a) memset(a, 0x3f, sizeof(a))
#define rep(i, n, a) for(int i = a; i<n; i++)
#define fi first
#define se second
typedef pair<int, int> pll;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int mod = 1e9+7;
const int inf = 1061109567;
const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
const int maxn = 2e4+5;
int sa[maxn];
int t1[maxn],t2[maxn],c[maxn], a[maxn];
int rankk[maxn],height[maxn], ans;
void build_sa(int s[],int n,int m)
{
    int i,j,p,*x=t1,*y=t2;
    for(i=0;i<m;i++)c[i]=0;
    for(i=0;i<n;i++)c[x[i]=s[i]]++;
    for(i=1;i<m;i++)c[i]+=c[i-1];
    for(i=n-1;i>=0;i--)sa[--c[x[i]]]=i;
    for(j=1;j<=n;j<<=1)
    {
        p=0;
        for(i=n-j;i<n;i++)y[p++]=i;
        for(i=0;i<n;i++)if(sa[i]>=j)y[p++]=sa[i]-j;
        for(i=0;i<m;i++)c[i]=0;
        for(i=0;i<n;i++)c[x[y[i]]]++;
        for(i=1;i<m;i++)c[i]+=c[i-1];
        for(i=n-1;i>=0;i--)sa[--c[x[y[i]]]]=y[i];
        swap(x,y);
        p=1;x[sa[0]]=0;
        for(i=1;i<n;i++)
            x[sa[i]]=y[sa[i-1]]==y[sa[i]] && y[sa[i-1]+j]==y[sa[i]+j]?p-1:p++;
        if(p>=n)break;
        m=p;
    }
}
void getHeight(int s[],int n)
{
    int i,j,k=0;
    for(i=0;i<=n;i++)rankk[sa[i]]=i;
    for(i=0;i<n;i++)
    {
        if(k)k--;
        j=sa[rankk[i]-1];
        while(s[i+k]==s[j+k])k++;
        height[rankk[i]]=k;
    }
}
int cal(int x, int n) {
    int minn  = sa[1], maxx = sa[1];
    int flag = 0;
    for(int i = 2; i<=n; i++) {
        if(height[i]<x) {
            if(maxx-minn>=x)
                ans++;
            maxx = minn = sa[i];
            flag = 1;
        } else {
            maxx = max(maxx, sa[i]);
            minn = min(minn, sa[i]);
        }
    }
    if(maxx-minn>=x)
        ans++, flag = 1;
    return flag;
}
int main()
{
    string s;
    while(cin>>s) {
        if(s[0] == '#')
            break;
        ans = 0;
        for(int i = 0; i<s.size(); i++)
            a[i] = s[i]-'a'+1;
        a[s.size()] = 0;
        build_sa(a, s.size()+1, 30);
        getHeight(a, s.size());
        for(int i = 1; i<=(s.size()+1)/2; i++) {
            if(!cal(i, s.size()))
                break;
        }
        cout<<ans<<endl;
    }
    return 0;
}