poj 3294 Life Forms (后缀数组)

http://poj.org/problem?id=3294

依旧二分判定，只是要先找出最大长度，然后在根据这个长度再判定输出。对于长度相同的，用tag标记以免重复。

code:

#include<cstdio>//最长公共子串
#include<cstring>
#define Max(a, b) a>b?a:b
const int maxn = 101001 ;
int wa[maxn], wb[maxn], wv[maxn], ws[maxn], rank[maxn], height[maxn], sa[maxn], s[maxn], loc[maxn] ;
bool vis[1001] ;
char str[1001], ans[1001] ;
int n ;
int cmp(int *r,int a,int b,int l){
return r[a]==r[b] && r[a+l]==r[b+l] ;
}
int abs(int a){
return a<0?-a:a ;
}
void da(int *r, 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 ++ ;
}
return ;
}
void calheight(int *r, int n){
int i, j, k = 0 ;
for(i=1; i<=n; i++) rank[sa[i]] = i ;//获取rank值 O(n)
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++) ;
return ;
}
int check(int mid, int len){
int count = 0 ;
memset(vis, false, sizeof(vis)) ;
for(int i=2; i<=len; i++){
if(height[i]<mid){
memset(vis, false, sizeof(vis)) ;
count = 0 ;
continue ;
}
if(!vis[loc[sa[i-1]]]) vis[loc[sa[i-1]]] = true, count ++ ;
if(!vis[loc[sa[i]]]) vis[loc[sa[i]]] = true, count ++ ;
if(count>n/2) return 1 ;
}
return 0 ;
}
void print(int mid, int len){
int count = 0, tag = 0 ;
memset(vis, false, sizeof(vis)) ;
for(int i=2; i<=len; i++){
if(height[i]<mid){
memset(vis, false, sizeof(vis)) ;
count = 0 ;
tag = 0 ;
continue ;
}
if(!vis[loc[sa[i-1]]]) vis[loc[sa[i-1]]] = true, count ++ ;
if(!vis[loc[sa[i]]]) vis[loc[sa[i]]] = true, count ++ ;
if(count>n/2&&!tag){
for(int j=0; j<mid; j++)
ans[j] = s[sa[i]+j] + 'a' - 1 ;
ans[mid] = '\0' ;
printf("%s\n", ans) ;
tag = 1 ;
}
}
}
int main(){
int i, j, m, max, t, flag, x, temp, min ;
while(~scanf("%d", &n)&&n){
flag = 0 ;
m = 0 ;
min = maxn ;
temp = 30 ;
for(i=0; i<n; i++){
scanf("%s", str) ;
if(strlen(str)<min) min = strlen(str) ;
for(j=0; str[j]; j++){
s[m] = str[j] - 'a' + 1 ;
loc[m++] = i ;
}
s[m] = temp ;
loc[m++] = temp ++ ;
}
s[m] = 0 ;
da(s, m+1, temp) ;
calheight(s, m) ;
int left=0, right=min, mid ;
while(right>=left){
mid = (right + left) / 2 ;
if(check(mid, m)){
left = mid + 1 ;
flag = mid ;
}
else
right = mid - 1 ;
}
if(flag){
print(flag, m) ;
printf("\n") ;
}
else
printf("?\n\n") ;
}
return 0 ;}