cf 427D Match & Catch 后缀数组

来源：互联网发布：虚拟币交易软件编辑：程序博客网时间：2024/05/01 10:37

将两个字符串连接，中间加一个没出现的字符，最后添加0。然后从小到大枚举长度ans，对于每个ans，对height数组分组，答案只可能出现在某组内，对每组进行检查，如果只存在两个字符串一个在前一个在后则return true，贴的代码是别人的。

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 100010;char s[maxn];int sa[maxn];int t[maxn], t2[maxn], c[maxn];int rank[maxn], height[maxn];int l1, l2;void build_sa(int m, int n){    int i, *x = t, *y = t2;    for(i = 0; i < m; i++)        c[i] = 0;    for(i = 0; i < n; i++)        c[x[i] = s[i]]++;    for(i = 1; i < m; i++)        c[i] += c[i-1];    for(i = n-1; i >= 0; i--)        sa[--c[x[i]]] = i;    for(int k = 1; k <= n; k <<= 1)    {        int p = 0;        for(i = n-k; i < n; i++)            y[p++] = i;        for(i = 0; i < n; i++)            if(sa[i] >= k)                y[p++] = sa[i] - k;        for(i = 0; i < m; i++)            c[i] = 0;        for(i = 0; i < n; i++)            c[x[y[i]]]++;        for(i = 0; 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]] = y[sa[i-1]] == y[sa[i]] && y[sa[i-1]+k] == y[sa[i]+k] ? p-1 : p++;        if(p >= n)            break;        m = p;    }}void getHeight(int n){    int k = 0;    for(int i = 0; i <= n; i++)        rank[sa[i]] = i;    for(int i = 0; i < n; i++)    {        if(k)            k--;        int j = sa[rank[i]-1];        while(s[i+k] == s[j+k])            k++;        height[rank[i]] = k;    }}bool ok(int m, int n){    int cnt1 = 0, cnt2 = 0;    for(int i = 1; i <= n; i++)    {        if(height[i] >= m)        {            if(sa[i-1] < l1)                cnt1++;            if(sa[i-1] > l1)                cnt2++;        }        else        {            if(sa[i-1] < l1)                cnt1++;            if(sa[i-1] > l1)                cnt2++;            if(cnt1 == 1 && cnt2 == 1)                return true;            cnt1 = cnt2 = 0;        }    }    return false;}int main(){    char a[5555], b[5555];    while(scanf("%s %s", &a, &b) != EOF)    {        l1 = strlen(a);        l2 = strlen(b);        int n = 0;        for(int i = 0; i < l1; i++)            s[n++] = a[i];        s[n++] = 'z'+1;        for(int i = 0; i < l2; i++)            s[n++] = b[i];        s[n] = 0;        build_sa(128, n+1);        getHeight(n);                int l = 1, r = 5000;        int ans = -1;        int len = min(l1, l2);        for(int i = 1; i <= len; i++)            if(ok(i, n))            {                ans = i;                break;            }        if(ans <= 0)            printf("-1\n");        else            printf("%d\n", ans);    }    return 0;}

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