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 + 5;
 
int getint();
 
int n, m, st;
int a[N], next[N], cnt[15];
 
int main() {
    int i, j;
    n = getint(), m = getint();
    for (i = 1; i <= n; ++i) ++cnt[(a[i] = getint()) + 1];
    for (i = 1; i <= m; ++i) cnt[i] += cnt[i - 1];
    for (i = 1; i <= n; ++i) next[++cnt[a[i]]] = i;
    for (i = st = 1; i <= n; ++i) if (a[i] < a[st]) st = i;
    for (i = 1, j = st; i <= n; ++i) printf("%d%c", a[j], i == n ? '
' : ' '), j = next[j];
    return 0;
}
 
const int BUF_SIZE = 30;
char buf[BUF_SIZE], *buf_s = buf, *buf_t = buf + 1;
#define isdigit(x) ('0' <= x && x <= '9')
#define PTR_NEXT() { 
    if (++buf_s == buf_t) 
        buf_s = buf, buf_t = buf + fread(buf, 1, BUF_SIZE, stdin); 
}
 
inline int getint() {
    register int x = 0;
    while (!isdigit(*buf_s)) PTR_NEXT();
    while (isdigit(*buf_s)) {
        x = x * 10 + *buf_s - '0';
        PTR_NEXT();
    }
    return x;
}

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