(Relax 后缀数组1.3)POJ 3415 Common Substrings(求串A和串B中长度不小于k的公共子串数)

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <string>

#define Fup(i, s, t) for (int i = s; i <= t; i ++)
#define Fdn(i, s, t) for (int i = s; i >= t; i --)
#define Path(i, s) for (int i = s; i; i = d[i].next)

using namespace std;

const int maxn = 200010;
struct number {
int x;
int pos;
} num[maxn];

struct node {
int now;
int next;

} d[maxn];

int val[maxn][2];
int c[maxn];
int rank[maxn];
int sa[maxn];
int pos[maxn];
int x[maxn];
int n;

int k;

int h[maxn];
int height[maxn];

string S,s;

int sta[maxn], num1[maxn], num2[maxn];
bool cmp(const number& a, const number& b) {
return a.x < b.x;
}

void add_value(int u, int v, int i) {
d[i].next = c[u];
c[u] = i;
d[i].now = v;
}

void radix_sort(int l, int r) {
for (int k = 1; k >= 0; --k) {

memset(c, 0, sizeof(c));
for (int i = r; i >= l; --i) {
add_value(val[pos[i]][k], pos[i], i);
}
int t = 0;
for (int i = 0; i <= 200000; ++i) {
for (int j = c[i]; j; j = d[j].next) {
pos[++t] = d[j].now;
}
}
}
int t = 0;
for (int i = 1; i <= n; ++i) {
if (val[pos[i]][0] != val[pos[i - 1]][0]
|| val[pos[i]][1] != val[pos[i - 1]][1]) {
t++;
}
rank[pos[i]] = t;
}
}

bool exist(int len) {
int now = 0;
int s = 0;
for (int i = 1; i <= n; ++i) { //枚举名次数组...
if (height[i] < len) {
s = max(s, now); //结束当前组
now = 1; //now恢复为1
} else {
now++;
}
}
s = max(s, now);

if (s >= k) {
return 1;
}
return 0;
}

void get_suffix_array() {
int t = 1;
while (t / 2 <= n) {
for (int i = 1; i <= n; ++i) {

val[i][0] = rank[i];
val[i][1] = (((i + t / 2 <= n) ? rank[i + t / 2] : 0));
pos[i] = i;
}
radix_sort(1, n);
t *= 2;
}
for (int i = 1; i <= n; ++i) {
sa[rank[i]] = i;
}
}

void get_common_prefix() {
memset(h, 0, sizeof(h));
for (int i = 1; i <= n; ++i) {

if (rank[i] == 1) {
h[i] = 0;
} else {
int now = 0;
if (i > 1 && h[i - 1] > 1) {
now = h[i - 1] - 1;
}
while (now + i <= n && now + sa[rank[i] - 1] <= n
&& x[now + i] == x[now + sa[rank[i] - 1]]) {
now++;
}
h[i] = now;
}
}
for (int i = 1; i <= n; ++i) {
height[rank[i]] = h[i];
}
}

int binary_search(int l, int r) {
while (l <= r) {
int mid = (l + r) / 2;
if (exist(mid)) {
l = mid + 1;
} else {
r = mid - 1;
}
}
return r;
}

void get_ans() {
Fup(i, 2, n)
height[i] -= k - 1;
long long sum1 = 0, sum2 = 0, ans = 0;
int top = 0;
Fup(i, 2, n)
if (height[i] <= 0) {
top = sum1 = sum2 = 0;
} else {
sta[++top] = height[i];
if (sa[i - 1] <= (int) S.size()) {
num1[top] = 1;
num2[top] = 0;
sum1 += (long long) sta[top];
} else {
num1[top] = 0;
num2[top] = 1;
sum2 += (long long) sta[top];
}
while (top > 0 && sta[top] <= sta[top - 1]) {
sum1 = sum1 - (long long) sta[top - 1] * num1[top - 1]
+ (long long) sta[top] * num1[top - 1];
sum2 = sum2 - (long long) sta[top - 1] * num2[top - 1]
+ (long long) sta[top] * num2[top - 1];
num1[top - 1] += num1[top];
num2[top - 1] += num2[top];
sta[top - 1] = sta[top];
top--;
}
if (sa[i] <= (int) S.size())
ans += sum2;
else
ans += sum1;
}
cout << ans << endl;
}

void init() {
cin >> S >> s;
n = (int) S.size() + s.size() + 1;
string str = S + '$' + s;
Fup(i, 1, n)
x[i] = rank[i] = (int) str[i - 1];
}

void solve() {
get_suffix_array();
get_common_prefix();
get_ans();
}

int main(){
while(scanf("%d",&k)!=EOF,k){
init();
solve();
}

return 0;
}