leetcode

commit d8d12c24604d7ac3d5382998cc9550e503726d1e
parent dc009d327e278bea38e4c981404a897accf278b8
Author: Jack Sangdahl <jack@pngu.org>
Date:   Wed, 27 May 2026 09:09:37 -0600

3121. count the number of special characters 2

Diffstat:
A
count_num_special_char2.c
 | 
40
++++++++++++++++++++++++++++++++++++++++
A
count_num_special_char2.py
 | 
25
+++++++++++++++++++++++++

2 files changed, 65 insertions(+), 0 deletions(-)
diff --git a/count_num_special_char2.c b/count_num_special_char2.c
@@ -0,0 +1,40 @@
+// 3121. Count the Number of Special Characters II
+#include "leetcode.h"
+
+/*
+ * you are given a string 'word'. a letter 'c' is called special if it appears
+ * both in lowercase and uppercase in 'word', and every lowercase occurence of
+ * 'c' appears before the first uppercase occurence of 'c'. return the number of
+ * special letters in 'word'.
+ */
+
+int numberOfSpecialChars(char *word) {
+  uint32_t lower = 0, upper = 0, invalid = 0;
+  for (int i = 0; word[i] != '\0'; i++) {
+    char curr = word[i];
+    bool lowercase = curr > 'Z';
+    int idx = curr - 'A' - (lowercase << 5);
+    if (lowercase)
+      lower |= (1 << idx);
+    else
+      upper |= (1 << idx);
+    invalid |= ((uint32_t)lowercase << idx) & upper;
+  }
+  uint32_t common = lower & upper & ~invalid;
+  return __builtin_popcount(common);
+}
+
+int main() {
+  char *w1 = "aaAbcBC";
+  char *w2 = "abc";
+  char *w3 = "AbBCab";
+  int r1 = numberOfSpecialChars(w1);
+  int r2 = numberOfSpecialChars(w2);
+  int r3 = numberOfSpecialChars(w3);
+  printf("%d\n", r1);
+  assert(r1 == 3);
+  printf("%d\n", r2);
+  assert(r2 == 0);
+  printf("%d\n", r3);
+  assert(r3 == 0);
+}
diff --git a/count_num_special_char2.py b/count_num_special_char2.py
@@ -0,0 +1,25 @@
+# 3121. Count the Number of Special Characters II
+from string import ascii_lowercase
+
+"""
+you are given a string 'word'. a letter 'c' is called special if it appears
+both in lowercase and uppercase in 'word', and every lowercase occurence of
+'c' appears before the first uppercase occurence of 'c'. return the number of
+special letters in 'word'.
+"""
+
+
+class Solution:
+    def numberOfSpecialChars(self, word: str) -> int:
+        d = {j: i for i, j in enumerate(word) if j.islower()}
+        p = {j: len(word) - i for i, j in enumerate(reversed(word)) if j.isupper()}
+        return sum(
+            d.get(i, float("inf")) < p.get(i.upper(), 0) for i in ascii_lowercase
+        )
+
+
+if __name__ == "__main__":
+    obj = Solution()
+    print(obj.numberOfSpecialChars(word="aaAbcBC"))
+    print(obj.numberOfSpecialChars(word="abc"))
+    print(obj.numberOfSpecialChars(word="AbBCab"))