hdu-1403-Longest Common Substring

#include <stdio.h>
#include <math.h>
#include <string.h>
#include <algorithm>
using namespace std;

const int N = 200010;

int r
, tx
, ty
, rs
, ranks
, sa
, height
, rmq
[20]; //rs基数排序
char s
;

bool cmp(int *r, int a, int b, int len)
{
return (r[a] == r[b]) && (r[a + len] == r[b + len]);
}

void suffix(int n, int m) //n为长度，最大值小于m
{
int i, j, p, *x = tx, *y = ty, *t;
for(i = 0; i < m; ++i)
rs[i] = 0;
for(i = 0; i < n; ++i) {
x[i] = r[i];
++rs[x[i]];
}
for(i = 1; i < m; ++i)
rs[i] += rs[i - 1];
for(i = n - 1; i >= 0; --i)
sa[--rs[x[i]]] = i;
for(j = p = 1; p < n; j <<= 1, m = p) {
for(p = 0, 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)
rs[i] = 0;
for(i = 0; i < n; ++i)
++rs[x[y[i]]];
for(i = 1; i < m; ++i)
rs[i] += rs[i - 1];
for(i = n - 1; i >= 0; --i)
sa[--rs[x[y[i]]]] = y[i];
t = x, x = y, y = t;
for(i = 1, p = 1, x[sa[0]] = 0; i < n; ++i) {
if(cmp(y, sa[i - 1], sa[i], j))
x[sa[i]] = p - 1;
else
x[sa[i]] = p++;
}
}
/**for(i = 0; i < n; ++i)
printf("%s\n", s + sa[i]);*/
}

void calheight(int n)
{
int i, j, k = 0;
for(i = 1; i <= n; ++i)
ranks[sa[i]] = i;
for(i = 0; i < n; ++i) {
if(k)
--k;
j = sa[ranks[i] - 1];
while(r[i + k] == r[j + k])
++k;
height[ranks[i]] = k;
}
}

void initrmq(int n)
{
int i, k;
for(i = 2; i <= n; ++i)
rmq[i][0] = height[i];
for(k = 1; (1 << k) <= n; ++k) {
for(i = 2; i + (1 << k) - 1 <= n; ++i) {
rmq[i][k] = min(rmq[i][k - 1],
rmq[i + (1 << (k - 1))][k - 1]);
}
}
}

int lcp(int a, int b)
{
a = ranks[a], b = ranks[b];
if(a > b)
swap(a, b);
++a;
int k = (int) (log((b - a + 1) * 1.0) / log(2.0));
return min(rmq[a][k], rmq[b - (1 << k) + 1][k]);
}

//求两个串的最长公共子串
int main()
{
int i, l1, n, ans;
while(scanf("%s", s)!=EOF){
l1 = strlen(s);
s[l1] = 1;
scanf("%s", s + l1 + 1);
n = strlen(s);
for(i = 0; i < n; ++i)
r[i] = s[i];
r
= 0;//便于比较
suffix(n + 1, 128);
calheight(n);
//initrmq(n);
ans = 0;
for(i = 2; i <= n; ++i) {
if((height[i] > ans) &&
((sa[i - 1] < l1 && sa[i] > l1) ||
(sa[i - 1] > l1 && sa[i] < l1)))
ans = height[i];
}
printf("%d\n", ans);
}
return 0;
}