hdu 4641 K-string（后缀自动机 + 并查集）

题目链接：hdu 4641 K-string

代码

#include 
#include 
#include 

using namespace std;
typedef long long ll;
const int maxn = 300005;
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], cnt[maxn<<1];
    int ridx[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 f[maxn<<1], sub[maxn<<1];
    int find(int x) { return x == f[x] ? x : f[x] = find(f[x]); }

    ll ans[maxn];
    void solve(int m, int* op, int k);
}SA;

int N, M, K, op[maxn];
char str[maxn];

void init () {
    SA.init();

    scanf("%s", str);
    for (int i = 0; i < N; i++)
        SA.insert(str[i]);

    char tmp[5];
    for (int i = 1; i <= M; i++) {
        scanf("%d", &op[i]);
        if (op[i] == 1) {
            scanf("%s", tmp);
            str[N++] = tmp[0];
            SA.insert(tmp[0]);
        }
    }
    str[N] = '\0';
    SA.get_tuopu();
    SA.get_right(str);
}

int main () {
    while (scanf("%d%d%d", &N, &M, &K) == 3) {
        init();
        SA.solve(M, op, K);
    }
    return 0;
}

void SAM::solve(int m, int* op, int k) {
    ll ret = 0;
    for (int i = 0; i < sz; i++) {
        int u = pos[i];
        if (right[u] >= k) ret += step[u] - step[pre[u]];
    }
    for (int i = 0; i <= sz; i++) f[i] = i, sub[i] = 0;

    for (int i = m; i; i--) {
        if (op[i] == 2) ans[i] = ret;
        else {
            int p = ridx[N--];
            int fp = find(p);
            while (fp && right[fp] < k) {
                p = f[fp] = pre[fp];
                fp = find(p);
            }

            if (fp == 0) continue;
            sub[fp]++;
            while (fp && right[fp] - sub[fp] < k) {
                ret -= step[fp] - step[pre[fp]];
                p = f[fp] = pre[fp];
                sub[pre[fp]] += sub[fp];
                fp = find(p);
            }
        }
    }
    for (int i = 1; i <= m; i++)
        if (op[i] == 2) printf("%lld\n", ans[i]);
}

void SAM::insert(char ch) {
    newNode(step[last] + 1);
    int v = idx(ch), p = last, np = sz;
    ridx[N] = np; //

    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];
    }
}