BZOJ2408 混乱的置换

这道题即THUSC 2015 t3...只不过数据范围$n, m ≤ 10^5$

可以上网查这个鬼畜的东西"Burrows-Wheeler Transform"

这道题要用到解压缩也就是IBWT算法，复杂度$O(n + m)$

 /**************************************************************
     Problem: 2408
     User: rausen
     Language: C++
     Result: Accepted
     Time:24 ms
     Memory:884 kb
 ****************************************************************/

 #include <cstdio>

 using namespace std;
 const int N = 1e4 + ;

 int getint();

 int n, m, st;
 int a[N], next[N], cnt[];

 int main() {
     int i, j;
     n = getint(), m = getint();
     for (i = ; i <= n; ++i) ++cnt[(a[i] = getint()) + ];
     for (i = ; i <= m; ++i) cnt[i] += cnt[i - ];
     for (i = ; i <= n; ++i) next[++cnt[a[i]]] = i;
     for (i = st = ; i <= n; ++i) if (a[i] < a[st]) st = i;
     for (i = , j = st; i <= n; ++i) printf("%d%c", a[j], i == n ? '\n' : ' '), j = next[j];
     return ;
 }

 const int BUF_SIZE = ;
 char buf[BUF_SIZE], *buf_s = buf, *buf_t = buf + ;
 #define isdigit(x) ('0' <= x && x <= '9')
 #define PTR_NEXT() { \
     if (++buf_s == buf_t) \
         buf_s = buf, buf_t = buf + fread(buf, , BUF_SIZE, stdin); \
 }

 inline int getint() {
     register int x = ;
     while (!isdigit(*buf_s)) PTR_NEXT();
     while (isdigit(*buf_s)) {
         x = x *  + *buf_s - '';
         PTR_NEXT();
     }
     return x;
 }

(p.s. 窝考试的时候sb。。。只想出来了$O(mn)$的算法QAQAQQQ)