minimum window substring solution

Author: hyer0705

minimum-window-substring/hyer0705.ts

@@ -0,0 +1,44 @@
+function minWindow(s: string, t: string): string {
+  const m = s.length;
+  const n = t.length;
+
+  if (m < n) return "";
+
+  let windowStart = 0;
+  let minLen = Infinity;
+  let substring = "";
+
+  let requiredChar = n;
+
+  const countCharMap = new Map<string, number>();
+  for (const ch of t) {
+    countCharMap.set(ch, (countCharMap.get(ch) || 0) + 1);
+  }
+
+  for (let windowEnd = 0; windowEnd < m; windowEnd++) {
+    const endChar = s[windowEnd];
+
+    if (countCharMap.has(endChar)) {
+      if (countCharMap.get(endChar)! > 0) requiredChar--;
+      countCharMap.set(endChar, (countCharMap.get(endChar) || 0) - 1);
+    }
+
+    while (requiredChar === 0) {
+      const currentLen = windowEnd - windowStart + 1;
+      if (currentLen < minLen) {
+        minLen = currentLen;
+        substring = s.substring(windowStart, windowEnd + 1);
+      }
+
+      const startChar = s[windowStart];
+      windowStart++;
+
+      if (countCharMap.has(startChar)) {
+        countCharMap.set(startChar, (countCharMap.get(startChar) || 0) + 1);
+        if (countCharMap.get(startChar)! > 0) requiredChar++;
+      }
+    }
+  }
+
+  return substring;
+}