Codeforces 427D Match & Catch（后缀自动机）

来源：互联网发布：炮王知乎编辑：程序博客网时间：2024/06/10 05:40
题目链接：Codeforces 427D Match & Catch
代码

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;typedef long long ll;const int maxn = 1e4 + 5;const int SIGMA_SIZE = 26;const int inf = 0x3f3f3f3f;struct SAM {    int sz, last;    int g[maxn<<1][SIGMA_SIZE], pre[maxn<<1], step[maxn<<1];    int pos[maxn<<1], right[maxn<<1], 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);    int solve (char* str) {        memset(cnt, 0, sizeof(cnt));        int p = 1, n = strlen(str);        for (int i = 0; i < n; i++) {            int v = idx(str[i]);            if (g[p][v]) p = g[p][v];            else {                while (p && g[p][v] == 0) p = pre[p];                if (p == 0) p = 1;                else p = g[p][v];            }            cnt[p]++;        }        for (int i = sz; i; i--) {            int u = pos[i];            cnt[pre[u]] += cnt[u];        }        int ret = inf;        for (int i = 2; i <= sz; i++) {            if (right[i] == 1 && cnt[i] == 1)                ret = min(ret, step[pre[i]] + 1);        }        if (ret == inf) ret = -1;        return ret;    }}SA;char a[maxn], b[maxn];int main () {    scanf("%s%s", a, b);    int n = strlen(a);    SA.init();    for (int i = 0; i < n; i++) SA.insert(a[i]);    SA.get_tuopu();    SA.get_right(a);    printf("%d\n", SA.solve(b));    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];    }}
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