hdu 1403 简单后缀数组应用

http://acm.hdu.edu.cn/showproblem.php?pid=1403 

题意：给两串字符，求最长的公共子串。

仔细想下就会想到后缀数组了。

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
using namespace std;
const int maxn = 220005;
int wn[maxn],wa[maxn],wb[maxn],wv[maxn],a[maxn],sa[maxn],rank[maxn],height[maxn];
char r[maxn];

int cmp(int *r,int a,int b,int l){ return r[a]==r[b]&&r[a+l]==r[b+l]; }
void da(int *r,int *sa,int n,int m)
{
    int i,j,p,*x=wa,*y=wb,*t;
    for(i = 0; i < m; ++ i) wn[i] = 0;
    for(i = 0; i < n; ++ i) wn[x[i]=r[i]]++;
    for(i = 1; i < m; ++ i) wn[i] += wn[i-1];
    for(i = n - 1; i >= 0; --i) sa[--wn[x[i]]] = i;
    for(p = 1,j = 1; p < n; j *= 2,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) wn[i] = 0;
        for(i = 0; i < n; ++ i) wn[wv[i]=x[y[i]]]++;
        for(i = 1; i < m; ++ i) wn[i] += wn[i-1];
        for(i = n - 1; i >= 0; --i) sa[--wn[wv[i]]] = y[i];
        for(t = x,x = y,y = t,x[sa[0]] = 0,p=1,i=1; i<n; ++i)
            x[sa[i]]=cmp(y,sa[i-1],sa[i],j)?p-1:p++;
    }
}
void calheight(int *r,int *sa,int n)
{
    int i,j,k = 0;
    for(i = 1; i <= n; ++ i){ rank[sa[i]] = i; height[i] = 0;}
    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);
}
int main()
{
    int i,j,k,n,m;
    while(scanf("%s",r)==1)
    {
        int L1 = strlen(r);
        r[L1] = '#';
        scanf("%s",r+L1+1);
        for(i = 0; r[i]; ++ i) a[i] = static_cast<int>(r[i]);
        a[i] = 0;
        da(a,sa,i+1,256);
        calheight(a,sa,i);
        k = 0; n = i;
        for(i = 2; i <= n; ++ i)
            if((sa[i]<L1)^(sa[i-1]<L1)) k = k>height[i]?k:height[i];
        printf("%d\n",k);
    }return 0;
}