feat: leetcode 828. Count Unique Characters of All Substrings of a Given String

Author: upupming

leetcode/残酷刷题/828. Count Unique Characters of All Substrings of a Given String.js

@@ -0,0 +1,19 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+const uniqueLetterString = function (s) {
+  const n = s.length; let ans = 0
+  for (let i = 0; i < 26; i++) {
+    const ch = String.fromCharCode('A'.charCodeAt(0) + i)
+    const pos = []
+    for (let i = 0; i < n; i++) {
+      if (s[i] === ch) pos.push(i)
+    }
+    for (let j = 0; j < pos.length; j++) {
+      const l = pos[j] - (pos[j - 1] ?? -1); const r = (pos[j + 1] ?? n) - pos[j]
+      ans += l * r
+    }
+  }
+  return ans
+}