|hdu 2328|后缀数组|二分|Corporate Identity

hdu 2328

给出n个字符串，输出他们的最长公共子串，无解输出”IDENTITY LOST”

用不同的符号连接每个字符串，然后二分公共子串的长度，在 height 数组中看有没有连续 n 个 height 大于公共子串的长度，如果有，那么更新答案。
(此题暴力比SA快，而且poj上用SA一直TLE，Hdu上1840ms就过了)

#include
#include
#include
#include
#define ms(i, j) memset(i, j, sizeof i)
#define FN2 "poj3450" 
using namespace std;

const int MAXN = 200 + 5, MAXT = 4000 + 5;

char s[MAXT][MAXN];
int t, n, m, ans[MAXN], ll, mini;
int a[MAXT*MAXN+200], SA[MAXT*MAXN+200], rk[MAXT*MAXN+200], tp[MAXT*MAXN+200], tax[MAXT*MAXN+200], height[MAXT*MAXN+200], belong[MAXT*MAXN+200];
bool cmp(int *f, int i, int k) {return f[SA[i]]==f[SA[i-1]]&&f[SA[i]+k]==f[SA[i-1]+k];}
void build() {
    for (int i=0;i0;
    for (int i=0;ifor (int i=1;i1];
    for (int i=n-1;i>=0;i--) SA[--tax[rk[i]]] = i;
    int p;
    for (int k=1;k<=n;k*=2) {
        p = 0;
        for (int i=n-k;ifor (int i=0;iif (SA[i]>=k) tp[p++] = SA[i] - k;

        for (int i=0;i0;
        for (int i=0;ifor (int i=1;i1];
        for (int i=n-1;i>=0;i--) SA[--tax[rk[tp[i]]]] = tp[i];

        swap(rk, tp), p = 0, rk[SA[0]] = 0;
        for (int i=1;iif (++p>=n) break;
        m = p;
    }
}
void getH() {
    int k = 0;
    for (int i=0;iif (k) k--;
        int j = SA[rk[i]-1];
        while (a[i+k]==a[j+k]) k++;
        height[rk[i]] = k;
    }
}
void init() {
    n = 0;
    int orz = 200;
    mini = 200000000;
    for (int i=0;iscanf("%s", s[i]);
        int l = strlen(s[i]); mini = min(mini, l);//取mini优化二分次数 
        for (int j=0;j1] = 0;
    m = orz + 5;
}
int used[MAXT];
bool check(int x) {
    int tot = 0;
    ms(used, false);
    for (int i=2;iif (height[i]0;
            ms(used, false);
            continue;
        }
        if (!used[belong[SA[i-1]]]) used[belong[SA[i-1]]] = true, ++tot;
        if (!used[belong[SA[i]]]) used[belong[SA[i]]] = true, ++tot;
        if (tot>=t) {
            int k = 0;
            for (int j=SA[i-1];j1]+height[i-1];j++) ans[k++] = a[j];
            return true;
        } 
    }
    return false;
}
void solve() {
    build(), getH();
    int l = 0, r = mini+1; ll = 0;//左闭右开，要+1！ 
/*  for (int i=0;i
    while (lint mid = (l+r)/2;
        if (check(mid)) {
            ll = mid;
            l = mid + 1;
        } else r = mid;
    }
    if (ll==0) printf("IDENTITY LOST\n");
     else {
        for (int i=0;iprintf("%c", ans[i]);
        printf("\n");
    }
}
int main() {
    #ifndef ONLINE_JUDGE
    freopen(FN2".in","r",stdin);freopen("1.out","w",stdout);
    #endif
    while(scanf("%d", &t)==1&t) init(), solve();
    return 0;
}

附上比SA快的暴力(可以对拍)

#include
#include
#include
#include
#define ms(i, j) memset(i, j, sizeof i)
#define FN2 "poj3450" 
using namespace std;

const int MAXN = 200 + 5, MAXT = 4000 + 5;

char s[MAXT][MAXN], ch[MAXN];
int t, n;

void init() {
    for (int i=0;iscanf("%s", s[i]);
    }   
    n = strlen(s[0]);
}
void solve() {
    int ans = 0;
    char fi[MAXN];
    for (int bg=0;bgfor (int end=bg;endint k = 0;
            int siz = end - bg + 1;
            if (sizcontinue;
            for (int i=0;i0; 
            for (int i=bg;i<=end;i++) ch[k++] = s[0][i];
            bool flag = false;
            for (int i=1;iif (!strstr(s[i], ch)) {flag = true; break;}
            if (!flag) {
                if (siz==ans&&strcmp(ch, fi)>=0) continue;
                memcpy(fi, ch, sizeof ch), ans = siz;
            }
        }
    }
    if (ans==0) printf("IDENTITY LOST\n");
    else printf("%s\n", fi);
}
int main() {
    #ifndef ONLINE_JUDGE
    freopen(FN2".in","r",stdin);freopen("2.out","w",stdout);
    #endif
    while(scanf("%d", &t)==1&&t) init(), solve();
    return 0;
}