[BZOJ 4044][Cerc2014]Virus synthesis

回文自动机学习

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#define maxn 100010using namespace std;int T;char str[maxn];int ans, n, Idx[300];struct Node{int nxt[4], fail, len, trans;void clear(){memset(nxt, 0, sizeof nxt);len = fail = trans = 0;}};int que[maxn], s[maxn];namespace PAM{Node st[maxn];int size, num, last, f[maxn];void init(){size = 1, num = 0, last = 0;st[0].clear(), st[1].clear();st[0].len = 0; st[1].len = -1;st[0].fail = st[1].fail = 1;s[0] = -1;}int get_fail(int x){while(s[num-st[x].len-1] != s[num])x = st[x].fail;return x;}void Insert(int c){s[++ num] = c;int cur = get_fail(last);if(!st[cur].nxt[c]){int now = ++ size; st[now].clear();st[now].len = st[cur].len + 2;st[now].fail = st[get_fail(st[cur].fail)].nxt[c];st[cur].nxt[c] = now;if(st[now].len <= 2)st[now].trans = st[now].fail;else{int o = st[cur].trans;while(s[num-st[o].len-1]!=s[num] || (st[o].len+2)*2 > st[size].len)    o = st[o].fail;st[now].trans = st[o].nxt[c];}}last = st[cur].nxt[c];}}int main(){using namespace PAM;Idx['A'] = 0, Idx['G'] = 1, Idx['C'] = 2, Idx['T'] = 3;int test;scanf("%d", &test);while(test --){scanf("%s", str+1);n = strlen(str+1);init(); ans = n;for(int i = 1; i <= n; i ++)    Insert(Idx[str[i]]);for(int i = 2; i <= size; i ++)if(st[i].len & 1)f[i] = st[i].len;int head = 0, tail = 0, t;que[tail ++] = 0;f[0] = 1;while(head != tail){int u = que[head ++];for(int i = 0; i < 4; i ++){if(t = st[u].nxt[i]){f[t] = min(f[u] + 1, st[t].len / 2 - st[st[t].trans].len + f[st[t].trans] + 1);ans = min(ans, n - st[t].len + f[t]);que[tail ++] = t;}}}printf("%d\n", ans);}}