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src/main/kotlin/p32xx/Problem3297.kt

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+package p32xx
+
+import util.expect
+
+fun main() {
+    class Solution {
+        fun validSubstringCount(word1: String, word2: String): Long {
+            var chars1 = IntArray(26)
+            var chars2 = IntArray(26)
+
+            var charKind = 0
+            word2.forEach {
+                val ch = it - 'a'
+                if (chars2[ch]++ == 0) {
+                    charKind++
+                }
+            }
+
+            var result = 0L
+            var left = 0
+            var right = 0
+            var matchKind = 0
+            while (right < word1.length || charKind == matchKind) {
+                if (charKind == matchKind) {
+                    val ch = word1[left++] - 'a'
+
+                    if (chars2[ch] > 0) {
+                        if (chars1[ch]-- == chars2[ch]) {
+                            matchKind--
+                        }
+                    }
+
+                } else {
+                    val ch = word1[right++] - 'a'
+
+                    if (chars2[ch] > 0) {
+                        if (++chars1[ch] == chars2[ch]) {
+                            matchKind++
+                        }
+                    }
+                }
+
+                if (charKind == matchKind) {
+                    result += word1.length - right + 1
+                }
+            }
+            return result
+        }
+    }
+
+    expect {
+        Solution().validSubstringCount(
+            "ddccdddccdddccccdddccdcdcd", "ddc"
+        )
+    }
+}