bzoj4199： [Noi2015]品酒大会 （并查集 && 后缀数组）

据说用后缀自动机 + dp也能做

然而并不会

后缀数组的做法呢

就是先建个后缀数组，求出height值，此时如果直接找，复杂度是n ^ 2的，肯定会超时。

但是height大的值是不会对小的产生影响的，所以可以按height大小，从大到小合并两个区间，用并查集维护就可以了

代码如下

 #include <cstdio>
 #include <algorithm>
 #include <cstring>
 using namespace std;
 const int N = ;
 typedef long long ll;
 char s[N];
 ll a[N];
 int n;
 int sa[N], c[N], x[N], y[N];

 struct E {
     int h, l, r;
     inline bool operator < (const E o) const {
         return h > o.h;
     }
 } g[N];
 inline void BuildSa(int m) {
     for (int i = ; i < m; i++)    c[i] = ;
     for (int i = ; i < n; i++)    c[x[i] = s[i]]++;
     for (int i = ; i < m; i++)    c[i] += c[i - ];
     for (int i = n - ; i >= ; i--)    sa[--c[x[i]]] = i;
     for (int k = ; k <= n; k <<= ) {
         int p = ;
         for (int i = n - k; i < n; i++)    y[p++] = i;
         for (int i = ; i < n; i++)    if (sa[i] >= k)    y[p++] = sa[i] - k;
         for (int i = ; i < m; i++)    c[i] = ;
         for (int i = ; i < n; i++)    c[x[y[i]]]++;
         for (int i = ; i < m; i++)    c[i] += c[i - ];
         for (int i = n - ; i >= ; i--)    sa[--c[x[y[i]]]] = y[i];
         p = ; swap(x, y);
         x[sa[]] = ;
         for (int i = ; i < n; i++)
             x[sa[i]] = y[sa[i]] == y[sa[i - ]] && y[sa[i] + k] == y[sa[i - ] + k] ? p -  : p++;
         if (p >= n)    break;
         m = p;
     }
 }

 int height[N], rank[N];
 inline void GetHeight() {
     for (int i = ; i < n; i++)    rank[sa[i]] = i;
     int k = ;
     for (int i = ; i < n; i++) {
         if (k)    k--;
         int j = sa[rank[i] - ];
         while (s[j + k] == s[i + k])    k++;
         height[rank[i]] = k;
     }
 }

 ll fa[N], size[N], ans[N], ans1[N], ans2[N], minn[N], maxn[N];
 void Union(int x, int y) {
     fa[x] = y;
     size[y] += size[x];
     ans[y] = max(ans[y], max(maxn[y] * maxn[x], minn[y] * minn[x]));
     maxn[y] = max(maxn[y], maxn[x]);
     minn[y] = min(minn[y], minn[x]);
 }

 int find(int x) {
     return (fa[x] == x) ? x : find(fa[x]);
 }

 int main() {
     scanf("%d", &n);
     getchar();
     for (int i = ; i < n; i++)
         scanf("%c", &s[i]), s[i] -= 'a' - ;
     for (int i = ; i < n; i++)
         scanf("%lld", &a[i]);
     s[n++] = ;
     BuildSa();
     GetHeight();
     for (int i = ; i < n; i++) {
         g[i].h = height[i];
         g[i].l = sa[i];
         g[i].r = sa[i - ];
     }
     sort(g + , g + n);
     for (int i = ; i < n; i++)    fa[i] = i, size[i] = , maxn[i] = a[i], minn[i] = a[i];
     memset(ans, 0x80, sizeof(ans));
     memset(ans2, 0x80, sizeof(ans2));
     for (int i = ; i < n; i++) {
         int x = find(g[i].l);
         int y = find(g[i].r);
         ans1[g[i].h] += (ll)size[x] * size[y];
         Union(x, y);
         ans2[g[i].h] = max(ans2[g[i].h], ans[y]);
     }
     for (int i = n - ; i >= ; i--) {
         ans1[i] += ans1[i + ];
         if (ans1[i + ])    ans2[i] = max(ans2[i], ans2[i + ]);
     }
     for (int i = ; i < n - ; i++)    printf("%lld %lld\n", ans1[i], ans1[i] ? ans2[i] : );
     return ;
 }