poj 1743 Musical Theme（后缀数组）

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题目链接：poj 1743 Musical Theme
代码

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 2 * 1e4 + 5;struct Suffix_Arr {    int n, s[maxn];    int SA[maxn], rank[maxn], height[maxn];    int tmp_one[maxn], tmp_two[maxn], c[205];    void init (int* t, int k);    void build(int m);    void getHeight();    bool judge(int m);    int solve();}AC;int N, A[maxn];int main () {    while (scanf("%d", &N) == 1 && N) {        for (int i = 0; i < N; i++) scanf("%d", &A[i]);        for (int i = 0; i < N-1; i++) A[i] = A[i+1] - A[i] + 89;        AC.init(A, N-1);        printf("%d\n", AC.solve());    }    return 0;}bool Suffix_Arr::judge(int m) {    int p = 1;    while (p < n) {        while (p < n && height[p] < m) p++;        if (p >= n) break;        int l = SA[p-1];        int r = SA[p-1];        while (p < n && height[p] >= m) {            l = min(l, SA[p]);            r = max(r, SA[p]);            p++;        }        if (r - l >= m) return true;    }    return false;}int Suffix_Arr::solve() {    build(200);    getHeight();    int l = 0, r = n / 2;    for (int i = 0; i < 100; i++) {        int mid = (l + r) >> 1;        if (judge(mid)) l = mid;        else r = mid;    }    if (l < 4) return 0;    return l + 1;}void Suffix_Arr::init(int* t, int k) {    n = 0;    for (int i = 0; i < k; i++)        s[n++] = t[i];    s[n++] = 0;}void Suffix_Arr::getHeight() {    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;    }}
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