【HDOJ】1403 Longest Common Substring

后缀数组2倍增可解。

#include <cstdio>
#include <cstring>
#include <cstdlib>

#define MAXM 28
#define MAXN 100010

int wa[MAXN*2];
int wb[MAXN*2];
int wv[MAXN*2];
int ws[MAXN*2];
char s[MAXN];
int str[MAXN*2], sa[MAXN*2];
int height[MAXN*2], rank[MAXN*2];

bool cmp(int *r, int a, int b, int l) {
    return r[a]==r[b] && r[a+l]==r[b+l];
}

void da(int *r, int *sa, int n, int m) {
    int i, j, *x = wa, *y = wb, *t;
    int p;
    
    for (i=0; i<m; ++i) ws[i] = 0;
    for (i=0; i<n; ++i) ws[x[i]=r[i]]++;
    for (i=1; i<m; ++i) ws[i] += ws[i-1];
    for (i=n-1; i>=0; --i) sa[--ws[x[i]]] = i;
    for (j=1, p=1; j<n; j*=2, m=p) {
        for (p=0, 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<n; ++i) wv[i] = x[y[i]];
        for (i=0; i<m; ++i) ws[i] = 0;
        for (i=0; i<n; ++i) ws[wv[i]]++;
        for (i=1; i<m; ++i) ws[i] += ws[i-1];
        for (i=n-1; i>=0; --i) sa[--ws[wv[i]]] = y[i];
        for (t=x, x=y, y=t, p=1, x[sa[0]]=0, i=1; i<n; ++i)
            x[sa[i]] = cmp(y, sa[i-1], sa[i], j) ? p-1:p++;
    }
}

void calheight(int *r, int *sa, int n) {
    int i, j, k=0;
    
    for (i=1; i<=n; ++i) rank[sa[i]] = i;
    for (i=0; i<n; height[rank[i++]]=k)
        for (k?k--:0, j=sa[rank[i]-1]; r[i+k]==r[j+k]; ++k)
            /*do nothing*/;
}

void printRank(int n) {
    int i;
    
    printf("
print rank...
");
    for (i=0; i<n; ++i)
        printf("%d ", rank[i]);
    printf("
");
}

void printSa(int n) {
    int i;
    
    printf("
print sa...
");
    for (i=0; i<n; ++i)
        printf("%d ", sa[i]);
    printf("
");
}

void printHeight(int n) {
    int i;
    
    printf("
print height...
");
    for (i=0; i<n; ++i)
        printf("%d ", height[i]);
    printf("
");
}

int main() {
    int l1, l2, l;
    int i, j, k;
    int ans;
    
#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif

    while (scanf("%s", s) != EOF) {
        l = 0;
        for (l1=0; s[l1]; l1++)
            str[l++] = s[l1] - 'a' + 2;
        str[l++] = 1;    // split two strings
        scanf("%s", s);
        for (l2=0; s[l2]; l2++)
            str[l++] = s[l2] - 'a' + 2;
        str[l] = 0;
        da(str, sa, l+1, MAXM);
        calheight(str, sa, l);
    #ifndef ONLINE_JUDGE
        printRank(l+1);
        printSa(l+1);
        printHeight(l);
    #endif
        ans = -1;
        for (i=2; i<=l; ++i) {
            if (height[i] > ans) {
                if ((sa[i-1]<l1 && sa[i]>l1) || (sa[i-1]>l1 && sa[i]<l1))
                    ans = height[i];
            }
        }
        printf("%d
", ans);
    }


    return 0;
}