20240418

ACMOJ-2121.cpp

@@ -0,0 +1,84 @@
+#include <algorithm>
+#include <cmath>
+#include <cstdio>
+#include <cstring>
+using namespace std;
+typedef long long LL;
+typedef long double LDB;
+const int kMaxN = (1 << 20) + 10;
+int T;
+char s[kMaxN];
+int z[kMaxN];
+int suf_cnt[26], pre_cnt[26];
+int tot_bucket[kMaxN];
+inline void Flip(char ch, int *cnt, int &occur) {
+  cnt[ch - 'a'] ^= 1;
+  if (cnt[ch - 'a'])
+    occur++;
+  else
+    occur--;
+}
+LL solve() {
+  int n = strlen(s);
+  memset(z, 0, sizeof(z));
+  for (int i = 1, l = 0, r = 0; i < n; ++i) {
+    if (i <= r && z[i - l] < r - i + 1) {
+      z[i] = z[i - l];
+    } else {
+      z[i] = max(0, r - i + 1);
+      while (i + z[i] < n && s[z[i]] == s[i + z[i]]) ++z[i];
+    }
+    if (i + z[i] - 1 > r) l = i, r = i + z[i] - 1;
+  }
+  LL res = 0;
+  int even_A_tot = 0;
+  int odd_A_tot = 0;
+  memset(suf_cnt, 0, sizeof(suf_cnt));
+  for (int i = 0; i < n; i++) suf_cnt[s[i] - 'a'] ^= 1;
+  int all_occur_tot = 0, suf_occur_tot = 0, pre_occur_tot = 0;
+  for (int i = 0; i < 26; i++) all_occur_tot += suf_cnt[i];
+  memset(pre_cnt, 0, sizeof(pre_cnt));
+  suf_occur_tot = all_occur_tot;
+  Flip(s[0], suf_cnt, suf_occur_tot);
+  memset(tot_bucket, 0, sizeof(tot_bucket));
+  for (int i = 1; i <= n - 1; i++) {
+    int odd_C_tot = ceil((min(z[i], n - i - 1) / i + 1) / 2.0);
+    int even_C_tot = ((min(z[i], n - i - 1) / i + 1) / 2.0);
+    res += odd_A_tot * (LL)odd_C_tot;
+    res += even_A_tot * (LL)even_C_tot;
+    // printf("A(%d,%d)\n", odd_A_tot, odd_C_tot);
+    // printf("B(%d,%d)\n", even_A_tot, even_C_tot);
+    if (i == n - 1) break;
+    int old_suf_occur_tot = suf_occur_tot;
+    Flip(s[i], suf_cnt, suf_occur_tot);
+    // Flip(s[i - 1], pre_cnt, pre_occur_tot, tot_bucket);
+    pre_cnt[s[i - 1] - 'a'] ^= 1;
+    if (pre_cnt[s[i - 1] - 'a']) {
+      pre_occur_tot++;
+    } else {
+      pre_occur_tot--;
+    }
+    tot_bucket[pre_occur_tot]++;
+    if (pre_occur_tot <= old_suf_occur_tot) odd_A_tot++;
+    if (old_suf_occur_tot < suf_occur_tot)
+      odd_A_tot += tot_bucket[suf_occur_tot];
+    else
+      odd_A_tot -= tot_bucket[old_suf_occur_tot];
+    // printf("i=%d all_occur_tot=%d pre_occur_tot=%d suf_occur_tot=%d\n", i,
+    //        all_occur_tot, pre_occur_tot, suf_occur_tot);
+    // odd_A_tot += (pre_occur_tot <= suf_occur_tot ? 1 : 0);
+    even_A_tot += (pre_occur_tot <= all_occur_tot ? 1 : 0);
+  }
+  return res;
+}
+int main() {
+#ifdef local
+  freopen("pro.in", "r", stdin);
+#endif
+  scanf("%d", &T);
+  while (T-- > 0) {
+    scanf("%s", s);
+    printf("%lld\n", solve());
+  }
+  return 0;
+}