POJ 3080 Blue Jeans

作为后缀数组的练习题，更好地理解后缀数组的用法，来写了这道题，应该是比life forms那道题更简单一点,整个程序结构和那道题几乎是一模一样的，这次更好地理解了check函数里面一些细节，比如记录位置变量i经常会在循环里面++了一次，下面在进行处理的时候就要人为地-1，这道题还是挺简单的，对后缀数组的用法又加深了印象。

#include <stdlib.h>
#include <cstdio>
#include <memory.h>
using namespace std;

#define maxn 1000
#define maxc 15
#define maxl 100

char DNA[maxc][maxl]={0};
int sa[maxn]={0}, height[maxn]={0}, rank[maxn]={0};
int wa[maxn]={0}, wb[maxn]={0}, ws[maxn]={0}, wv[maxn]={0};
int link[maxn]={0};
int st_en[maxc][2];

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

//计算后缀数组的模板
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++) ws[i] = 0;
for (i = 0; i<n; i++) ws[x[i] = r[i]]++;
for (i = 1; i<m; i++) ws[i] += ws[i - 1];
for (i = n - 1; i >= 0; i--) sa[--ws[x[i]]] = i;
for (j = 1, p = 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<n; i++) wv[i] = x[y[i]];
for (i = 0; i<m; i++) ws[i] = 0;
for (i = 0; i<n; i++) ws[wv[i]]++;
for (i = 1; i<m; i++) ws[i] += ws[i - 1];
for (i = n - 1; 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; i++)
x[sa[i]] = cmp(y, sa[i - 1], sa[i], j) ? p - 1 : p++;
}
}

//计算height数组模板
void calheight(int *r, int *sa, int n) {
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++);
}

int ID(int k, int n){
for(int i=0;i<n;++i){
if(k<=st_en[i][1]&&k>=st_en[i][0])
return i;
}
return -1;
}

bool check(int k,int n,int tcount,bool output = false){
int i=0;
int cnt = 0;
while(true){
bool visited[maxn]={0};
while(i<tcount&&height[i]<k)
++i;
if(i>=tcount)
break;

visited[ID(sa[i-1],n)] = 1;
cnt = 1;

while(i<tcount&&height[i]>=k){
if(!visited[ID(sa[i],n)]){
visited[ID(sa[i],n)] = true;
cnt++;
}
++i;
}

if(cnt>=n){
if(output){
for(int j=sa[i-1];j<k+sa[i-1];++j){
printf("%c",link[j]);
}
printf("\n");
}
return true;
}
}
return false;
}

int main(){
int t;
scanf("%d",&t);
while(t--){
memset(sa,0,sizeof(sa));
memset(height,0,sizeof(height));
memset(DNA,0,sizeof(DNA));
memset(rank,0,sizeof(rank));

int n;
scanf("%d",&n);

4000
for(int i=0;i<n;++i){
scanf("%s",DNA[i]);
}
int tcount = 0;
for(int i=0;i<n;++i){
st_en[i][0] = tcount;
for(int j=0;j<60;++j){
link[tcount++] = (int)DNA[i][j];
}
st_en[i][1] = tcount;
link[tcount++] = i;
}

DA(link,sa,tcount,200);
calheight(link,sa,tcount-1);

//printf("tcount: %d\n",tcount);

int left = 0, right = 60;
while(left<right){

int mid = (left + right + 1)>>1;
if(check(mid,n,tcount))
left = mid;
else
right = mid - 1;
}
//printf("left: %d\n",left);
if(left<3){
printf("no significant commonalities\n");
}
else{
check(left,n,tcount,true);
}

}
//system("pause");
return 0;
}