poj 2774 Long Long Message 后缀数组基础题

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = 1000000 + 10;
int t1[maxn], t2[maxn], c[maxn];
bool cmp(int *r, int a, int b, int l) {
    return r[a] == r[b] && r[a + l] == r[b + l];
}
void da(char str[], int sa[], int Rank[], int heigh[], int n, int m)
{
    n++;
    int i, j, p, *x = t1, *y = t2;
    for(i = 0; i < m; ++i) c[i] = 0;
    for(i = 0; i < n; ++i) c[ x[i] = str[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 j = 1; j <= n; j <<= 1)
    {
        p = 0;
        for(i = n - j; i < n; ++i) y[p++] = i;
        for(i = 0; i < n; ++i) if(sa[i] >= j) y[p++] = sa[i] - j;

        for(i = 0; i < m; ++i) c[i] = 0;
        for(i = 0; i < n; ++i) c[x[y[i]]]++;
        for(i = 1; i < m; ++i) c[i] += c[i - 1];
        for(i = n - 1; i >= 0; --i) sa[--c[x[y[i]]]] = y[i];
        swap(x, y);
        p = 1; x[ sa[0] ] = 0;
        for(i = 1; i < n; ++i)
            x[ sa[i] ] = cmp(y, sa[i - 1], sa[i], j) ? p - 1 : p++;
        if(p >= n) break;
        m = p;
    }
    int k = 0;
    n--;
    for(i = 0; i <= n; ++i) Rank[ sa[i] ] = i;
    for(i = 0; i < n; ++i) {
        if(k) k--;
        j = sa[Rank[i] - 1];
        while(str[i + k] == str[j + k]) k++;
        heigh[ Rank[i] ] = k;
    }
}

int Rank[maxn], heigh[maxn], sa[maxn];
char s[maxn], s2[maxn];
void out(int n) {
    puts("Rank[]");
    ///Rank数组的有效范围是0~n-1， 值是1~n
    for(int i = 0; i <= n; ++i) printf("%d ", Rank[i]);
    puts("sa[]");
    ///sa数组的有效范围是1~n，值是0~n-1
    for(int i = 0; i <= n; ++i) printf("%d ", sa[i]);
    puts("heigh[]");
    ///heigh数组的有效范围是2~n
    for(int i = 0; i <= n; ++i) printf("%d ", heigh[i]);
}
int ls;
bool check(int x, int n) {
    int mi = INF, mx = -INF;
    for(int i = 2; i <= n; ++i) {
        if(heigh[i] >= x) {
            mi = min(mi, min(sa[i - 1], sa[i]));
            mx = max(mx, max(sa[i - 1], sa[i]));
        }else {
            if(mi + x < ls && mx >= ls) return true;
            mi = INF, mx = -INF;
        }
    }
    if(mi + x < ls && mx > ls) return true;
    return false;
}
int solve(int n) {
    int L = 0, R = n + 1;
    while(R - L > 1) {
        int M = (L + R) >> 1;
        if(check(M, n)) L = M;
        else R = M;
    }
    return L;
}
int main() {
    while(~scanf("%s%s", s, s2))
    {
        ls = strlen(s);
        strcat(s, s2);
        int n = strlen(s);
        da(s, sa, Rank, heigh, n, 128);
        printf("%d\n", solve(n));
    }
    return 0;
}