20240418

ACMOJ-2112.cpp

@@ -0,0 +1,29 @@
+#include <algorithm>
+#include <cstdio>
+#include <cstring>
+#include <stack>
+using namespace std;
+const int kMaxN = 4e6 + 10;
+char s[kMaxN], s_reverse[kMaxN];
+int len = 0;
+int Next[kMaxN];
+int main() {
+#ifdef local
+  freopen("pro.in", "r", stdin);
+#endif
+  scanf("%s", s + 1);
+  len = strlen(s + 1);
+  for (int i = 1; i <= len; i++) s_reverse[i] = s[len + 1 - i];
+  for (int i = 2, j = 0; i <= len; i++) {
+    while (j > 0 && s_reverse[i] != s_reverse[j + 1]) j = Next[j];
+    if (s_reverse[i] == s_reverse[j + 1]) j++;
+    Next[i] = j;
+  }
+  int p = 0;
+  for (int i = 1; i <= len; i++) {
+    while (p > 0 && s[i] != s_reverse[p + 1]) p = Next[p];
+    if (s[i] == s_reverse[p + 1]) p++;
+  }
+  printf("%d\n", len - p);
+  return 0;
+}