SPOJ Lexicographical Substring Search 后缀自动机

给定一个字符串，取出所有的子串按照字典序排序并去重后，求第K大的子串。

以为自动机写错了。。后来发现是DP出的问题。 后缀自动机先告一段落，整理点东西出来吧！比赛时候出裸题，我得保证能做出来才行。

#include 
#include 
#include 
#include 
using namespace std;


const int CHAR = 26;
const int MAXN = 250000 * 2  + 100;
char str[MAXN];

bool duanyan(bool flag, const string &x)
{
	if (!flag)
	{
		cout << x << endl;
		throw 0;
		exit(0);
	}
}

struct SAM_Node
{
	SAM_Node *fa, *next[CHAR];
	int len;
	int id, pos;
	long long dp;
	SAM_Node(){}
	SAM_Node(int _len)
	{
		fa = 0;
		len = _len;
		dp=0;
		memset(next, 0, sizeof(next));
	}
};

SAM_Node SAM_node[MAXN *2], *SAM_root, *SAM_last;
int SAM_size;

SAM_Node * newSAM_Node(int len)
{
	SAM_node[SAM_size] = SAM_Node(len);
	SAM_node[SAM_size].id = SAM_size; 
	SAM_node[SAM_size].dp = 0; 
	return &SAM_node[SAM_size++];
}

SAM_Node *newSAM_Node(SAM_Node *p)
{
	SAM_node[SAM_size] = *p;
	SAM_node[SAM_size].id = SAM_size;
	SAM_node[SAM_size].dp = 0; 
	return &SAM_node[SAM_size++];
}

void SAM_init()
{
	SAM_size = 0;
	SAM_root = SAM_last = newSAM_Node(0);
	SAM_node[0].pos = 0;
}

void SAM_add(int x, int len)
{
	SAM_Node *p = SAM_last, *np = newSAM_Node(p -> len+1);
	np -> pos = len;
	SAM_last = np;
	for (;p && !p -> next[x]; p = p -> fa)
		p -> next[x] = np;
	if (!p)
	{
		np -> fa = SAM_root;
		return;
	}
	SAM_Node *q = p -> next[x];
	if (q -> len == p-> len+1)
	{
		np -> fa = q;
		return;
	}
	SAM_Node *nq = newSAM_Node(q);
	nq -> len = p -> len + 1;
	q -> fa = nq;
	np -> fa = nq;
	for (;p && p-> next[x] == q; p = p -> fa)
		p -> next[x] = nq;
}

int topcnt[MAXN];
SAM_Node *topsam[MAXN*2];

void SAM_build(char *s)
{
	SAM_init();
	int len = strlen(s);
	for (int i = 0 ;i < len; ++ i)
		SAM_add(s[i] - 'a' , i + 1);
}

int g[MAXN], f[MAXN];

void pg()
{

	for (int i = 0; i < SAM_size; ++ i)
	{
		cout <<"@"<< SAM_node[i].id<< endl;
		for (int j = 0; j < 26; ++ j)
		{
			if (SAM_node[i].next[j])
			{
				cout << SAM_node[i].next[j] -> id << endl;
			}
		}
		if (i)
		cout << "fa: " << SAM_node[i].fa -> id << endl;
		cout<<"===="< next[i])
			{
				if (k <= (now -> next[i] -> dp))
				{
					putchar(i+'a');	//	TODO
					now = now -> next[i];
					--k; //why here???
					break;
				}
				else
				{
					k -= now -> next[i] -> dp;
				}
			}
		}
	}
	putchar('\n');
}

int main()
{
	int t;
	scanf("%s", str);
	SAM_build(str);
	int n = strlen(str);

	memset(topcnt, 0, sizeof(topcnt));
	for (int i = 0; i < SAM_size; ++ i)
		topcnt[SAM_node[i].len] ++ ;
	for (int i = 1; i <= n; ++ i)
		topcnt[i] += topcnt[i - 1];
	for (int i = 0; i < SAM_size ; ++ i)
		topsam[-- topcnt[SAM_node[i].len]] = &SAM_node[i];
	for (int i = 1; i < SAM_size; ++ i)
		SAM_node[i].dp = 1;


	for (int i = SAM_size -1; i>=0; -- i)
	{
		SAM_Node *now = topsam[i];

		for (int i = 0; i < 26; ++ i)
		{
			if (now->next[i])
			{
				now->dp += now->next[i]->dp;
			}
		}
	}

	scanf("%d", &t);
	pg();
	while (t--)
	{
		long long k;
		scanf("%lld", &k);
		//if (k> SAM_root->dp)	continue;
		find(SAM_root, k);
		//cout<<"=========================="<