cf 427D Match & Catch 后缀数组

将两个字符串连接，中间加一个没出现的字符，最后添加0。然后从小到大枚举长度ans，对于每个ans，对height数组分组，答案只可能出现在某组内，对每组进行检查，如果只存在两个字符串一个在前一个在后则return true，贴的代码是别人的。

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 100010;
char s[maxn];
int sa[maxn];
int t[maxn], t2[maxn], c[maxn];
int rank[maxn], height[maxn];
int l1, l2;
void build_sa(int m, int n)
{
int i, *x = t, *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(int k = 1; k <= n; k <<= 1)
{
int p = 0;
for(i = n-k; i < n; i++)
y[p++] = i;
for(i = 0; i < n; i++)
if(sa[i] >= k)
y[p++] = sa[i] - k;
for(i = 0; i < m; i++)
c[i] = 0;
for(i = 0; i < n; i++)
c[x[y[i]]]++;
for(i = 0; 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]+k] == y[sa[i]+k] ? p-1 : p++;
if(p >= n)
break;
m = p;
}
}

void getHeight(int n)
{
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;
}
}

bool ok(int m, int n)
{
int cnt1 = 0, cnt2 = 0;
for(int i = 1; i <= n; i++)
{
if(height[i] >= m)
{
if(sa[i-1] < l1)
cnt1++;
if(sa[i-1] > l1)
cnt2++;
}
else
{
if(sa[i-1] < l1)
cnt1++;
if(sa[i-1] > l1)
cnt2++;
if(cnt1 == 1 && cnt2 == 1)
return true;
cnt1 = cnt2 = 0;
}
}
return false;
}
int main()
{
char a[5555], b[5555];
while(scanf("%s %s", &a, &b) != EOF)
{
l1 = strlen(a);
l2 = strlen(b);
int n = 0;
for(int i = 0; i < l1; i++)
s[n++] = a[i];
s[n++] = 'z'+1;
for(int i = 0; i < l2; i++)
s[n++] = b[i];
s
= 0;
build_sa(128, n+1);
getHeight(n);

int l = 1, r = 5000;
int ans = -1;
int len = min(l1, l2);
for(int i = 1; i <= len; i++)
if(ok(i, n))
{
ans = i;
break;
}
if(ans <= 0)
printf("-1\n");
else
printf("%d\n", ans);
}
return 0;
}