后缀数组，看到网上很多题解都是单调栈，这里提供一个不是单调栈的做法，
首先将两个串 连接起来求height 求完之后按height值从大往小合并。 height值代表的是 sa[i]和sa[i-1] 的公共前缀长度，那么每次合并就是合并 i和i-1 那么在合并小的时候公共前缀更大的肯定已经都合并在一起，那么就可以直接统计了。
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<vector>
#include<queue>
#include<map>
#include<set>
#include<time.h>
#include<string>
#define cl(a,b) memset(a,b,sizeof(a))
#define max(x,y) ((x)>(y)?(x):(y))
#define min(x,y) ((x)<(y)?(x):(y))
#define REP(i,n) for(int i=0;i<n;++i)
#define REP1(i,a,b) for(int i=a;i<=b;++i)
#define REP2(i,a,b) for(int i=a;i>=b;--i)
#define MP make_pair
#define LL long long
#define ULL unsigned long long
#define X first
#define Y second
using namespace std; const int MAXN = 200050; struct SuffixArray{
int wa[MAXN];
int wb[MAXN];
int wv[MAXN];
int ws[MAXN]; int sa[MAXN];
int rank[MAXN];
int height[MAXN];
int r[MAXN];
int n;
int m; void input(int *val, int len, int Max){
for (int i = 0;i < len;i++)
r[i] = val[i];
r[len] = 0;
n = len;
m = Max;
calSa();
calHeight();
} int cmp(int *r, int a, int b, int l){
return (r[a] == r[b] && r[a + l] == r[b + l]);
} void calSa(){
int i, j, p, *x = wa, *y = wb, *t;
for (i = 0;i < m;i++) ws[i] = 0;
for (i = 0;i < n + 1;i++) ws[x[i] = r[i]]++;
for (i = 1;i < m;i++) ws[i] += ws[i - 1];
for (i = n;i >= 0;i--) sa[--ws[x[i]]] = i;
for (j = 1, p = 1;p < n + 1;j *= 2, m = p){
for (p = 0, i = n - j + 1;i < n + 1;i++) y[p++] = i;
for (i = 0;i < n + 1;i++) if (sa[i] >= j) y[p++] = sa[i] - j;
for (i = 0;i < n + 1;i++) wv[i] = x[y[i]];
for (i = 0;i < m;i++) ws[i] = 0;
for (i = 0;i < n + 1;i++) ws[wv[i]]++;
for (i = 1;i < m;i++) ws[i] += ws[i - 1];
for (i = n;i >= 0;i--) sa[--ws[wv[i]]] = y[i];
for (t = x, x = y, y = t, p = 1, x[sa[0]] = 0, i = 1; i < n + 1;i++)
x[sa[i]] = cmp(y, sa[i - 1], sa[i], j) ? p - 1 : p++;
}
} void calHeight(){
int i, j, k = 0;
for (i = 1;i <= n;i++) rank[sa[i]] = i;
for (i = 0;i < n;height[rank[i++]] = k)
for (k?k--:0, j = sa[rank[i]- 1];r[i + k] == r[j + k];k++);
} }SA;
char s1[MAXN],s2[MAXN];
int s[MAXN];
vector<int>e[MAXN];
int id[MAXN];
int x[MAXN],y[MAXN];
int fa[MAXN];
int getfa(int x)
{
if(fa[x]==x)return x;
else
return fa[x]=getfa(fa[x]);
}
int main()
{
int k;
while(scanf("%d",&k)&&k)
{
int h=0,len1,len2;
scanf(" %s %s",s1,s2);
len1=strlen(s1);
len2=strlen(s2);
for(int i=0;i<len1;++i)
{
id[h]=0;
s[h++]=s1[i];
}
s[h++]=1;
for(int i=0;i<len2;++i)
{
id[h]=1;
s[h++]=s2[i];
}
SA.input(s,h,500);
// for(int i=0;i<=h;++i)
// printf("%d %d %d\n",i,SA.sa[i],SA.height[i]);
for(int i=0;i<=h;++i)
e[i].clear();
for(int i=1;i<=h;++i)
{
e[SA.height[i]].push_back(i);
}
for(int i=0;i<=h;++i)
{
fa[i]=i;
if(id[SA.sa[i]]==0)//这里要用sa来判断原先属于哪个串
x[i]=1,y[i]=0;
else
x[i]=0,y[i]=1;
}
LL ans=0;
for(int i=h;i>=k;--i)
{
for(int j=0;j<e[i].size();++j)
{
int u=e[i][j];
int f1=getfa(u);
int f2=getfa(u-1);
// printf("%d %d\n",f1,f2);
if(f1!=f2){
ans-=(LL)x[f2]*y[f2]*(i-k+1);//减去原先的贡献值
ans-=(LL)x[f1]*y[f1]*(i-k+1);//减去原先的贡献值
fa[f1]=f2;
x[f2]+=x[f1];
y[f2]+=y[f1];
ans+=(LL)x[f2]*y[f2]*(i-k+1);//加上新的
}
}
}
printf("%I64d\n",ans);
}
}