poj 2774 Long Long Message（后缀数组）

代码

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int maxn = 100005 * 4;

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 getHeight();
int solve(int p);
}AC;

char str[maxn], a[maxn];

int main () {
while (scanf("%s%s", str, a) == 2) {
int n = strlen(str);
str
= 'z' + 1;
str[n+1] = '\0';
strcat(str, a);
AC.init(str);
printf("%d\n", AC.solve(n));
}
return 0;
}

int Suffix_Arr::solve(int p) {
build(28);
getHeight();

int ret = 0;
for (int i = 1; i < n; i++) {
int l = SA[i-1];
int r = SA[i];
if ((l < p || r < p) && (l >= p || r >= p)) {
ret = max(ret, height[i]);
}
}
return ret;
}

void Suffix_Arr::init(char* str) {
n = 0;
int len = strlen(str);
for (int i = 0; i < len; i++)
s[n++] = str[i] - 'a' + 1;
s[n++] = 0;
}

/*
void Suffix_Arr::rmq_init() {
for (int i = 0; i < n; i++) d[i][0] = height[i];

for (int k = 1; (1<<k) <= n; k++) {
for (int i = 0; i + (1<<k) - 1 < n; i++)
d[i][k] = min(d[i][k-1], d[i+(1<<(k-1))][k-1]);
}
}

int Suffix_Arr::rmq_query(int x, int y) {
if (x == y)
return d[x][0];
if (x > y)
swap(x, y);
x++;
int k = 0;
while ((1<<(k+1) <= y - x + 1)) k++;
return min(d[x][k], d[y - (1<<k) + 1][k]);
}
*/
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;
}
}