spoj 7258 Lexicographical Substring Search（后缀数组 | 后缀自动机）

题目链接：spoj 7258 Lexicographical Substring Search

代码 - 后缀数组

#include <cstdio>#include <cstring>#include <stack>#include <vector>#include <algorithm>using namespace std;const int maxn = 90000 + 5;struct Suffix_Arr {    int n, s[maxn];    int SA[maxn], rank[maxn], height[maxn];    int tmp_one[maxn], tmp_two[maxn], c[305];    void init(char* str);    void build(int m);    void get_height();    int f[maxn];    void solve();    void query(char* str, int k);}SFA;char str[maxn];int main () {    scanf("%s", str);    SFA.init(str);    int q, k;    SFA.solve();    scanf("%d", &q);    while (q--) {        scanf("%d", &k);        SFA.query(str, k);    }    return 0;}void Suffix_Arr::init(char* str) {    n = 0;    int len = strlen(str);    for (int i = 0; i < len; i++)        s[n++] = str[i];    s[n++] = 0;}void Suffix_Arr::query(char* str, int k) {    int idx = lower_bound(f, f + n, k) - f;    int bw = k - f[idx-1] + height[idx], s = SA[idx];    for (int i = 0; i < bw; i++)        printf("%c", str[s+i]);    printf("\n");}void Suffix_Arr::solve() {    build(300);    get_height();    f[0] = 0;    for (int i = 1; i < n; i++)        f[i] = f[i-1] + (n - 1 - SA[i] - height[i]);}void Suffix_Arr::get_height() {    for (int i = 0; i < n; i++)        rank[SA[i]] = i;    int mv = height[0] = 0;    for (int i = 0; i < n - 1; i++) {        if (mv) mv--;        int j = SA[rank[i]-1];        while (s[i+mv] == s[j+mv]) mv++;        height[rank[i]] = mv;    }}void Suffix_Arr::build(int m) {    int* x = tmp_one, *y = tmp_two;    for (int i = 0; i < m; i++) c[i] = 0;    for (int i = 0; i < n; i++) c[x[i] = s[i]]++;    for (int i = 1; i < m; i++) c[i] += c[i-1];    for (int i = n - 1; i >= 0; i--) SA[--c[x[i]]] = i;    for (int k = 1; k <= n; k <<= 1) {        int mv = 0;        for (int i = n - k; i < n; i++) y[mv++] = i;        for (int i = 0; i < n; i++) if(SA[i] >= k)             y[mv++] = SA[i] - k;        for (int i = 0; i < m; i++) c[i] = 0;        for (int i = 0; i < n; i++) c[x[y[i]]]++;        for (int i = 1; i < m; i++) c[i] += c[i-1];        for (int i = n - 1; i >= 0; i--) SA[--c[x[y[i]]]] = y[i];        swap(x, y);        mv = 1;        x[SA[0]] = 0;        for (int i = 1; i < n; i++)            x[SA[i]] = (y[SA[i-1]] == y[SA[i]] && y[SA[i-1] + k] == y[SA[i] + k] ? mv - 1 : mv++);        if (mv >= n) break;        m = mv;    }}

代码-后缀自动机

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;typedef long long ll;const int maxn = 90005; const int SIGMA_SIZE = 26;struct SAM {    int sz, last;    int g[maxn<<1][SIGMA_SIZE], pre[maxn<<1], step[maxn<<1];    int pos[maxn<<1], right[maxn<<1];    ll cnt[maxn<<1];    void newNode(int s) {        step[++sz] = s;        pre[sz] = 0;        memset(g[sz], 0, sizeof(g[sz]));    }    int idx(char ch) { return ch -'a'; }    void init() {        sz = 0, last = 1;        newNode(0);    }    void insert(char ch);    void get_tuopu();    void get_right(char* str);    void presolve() {        get_tuopu();        for (int i = 1; i <= sz; i++) cnt[i] = 1;        for (int i = sz; i; i--) {            int u = pos[i];            for (int j = 0; j < SIGMA_SIZE; j++)                cnt[u] += cnt[g[u][j]];        }    }    void query(int k) {        int p = 1;        while (k) {            k--;            for (int i = 0; i < SIGMA_SIZE; i++) {                int u = g[p][i];                if (u == 0) continue;                if (cnt[u] <= k) k -= cnt[u];                else { printf("%c", i + 'a'); p = u; break; }            }        }        printf("\n");        /*        for (int i = 1; i <= sz; i++)            printf("%d %lld\n", i, cnt[i]);            */    }}SA;char str[maxn];int main () {    scanf("%s", str);    int n = strlen(str), k;    SA.init();    for (int i = 0; i < n; i++) SA.insert(str[i]);    SA.presolve();    scanf("%d", &n);    while (n--) {        scanf("%d", &k);        SA.query(k);    }    return 0;}void SAM::insert(char ch) {    newNode(step[last] + 1);    int v = idx(ch), p = last, np = sz;    while (p && !g[p][v]) {        g[p][v] = np;        p = pre[p];    }    if (p) {        int q = g[p][v];        if (step[q] == step[p] + 1)            pre[np] = q;        else {            newNode(step[p] + 1);            int nq = sz;            for (int j = 0; j < SIGMA_SIZE; j++) g[nq][j] = g[q][j];            pre[nq] = pre[q];            pre[np] = pre[q] = nq;            while (p && g[p][v] == q) {                g[p][v] = nq;                p = pre[p];            }        }    } else        pre[np] = 1;    last = np;}void SAM::get_tuopu() {    for (int i = 0; i <= sz; i++) cnt[i] = 0;    for (int i = 1; i <= sz; i++) cnt[step[i]]++;    for (int i = 1; i <= sz; i++) cnt[i] += cnt[i-1];    for (int i = 1; i <= sz; i++) pos[cnt[step[i]]--] = i; }void SAM::get_right(char* str) {    int p = 1, n = strlen(str);    for (int i = 0; i <= sz; i++) right[i] = 0;    for (int i = 0; i < n; i++) {        int v = idx(str[i]);        p = g[p][v];        right[p]++;    }    for (int i = sz; i; i--) {        int u = pos[i];        right[pre[u]] += right[u];    }}