Add minimum-window-substring solution in TS

Author: Jeehay28

minimum-window-substring/Jeehay28.ts

@@ -0,0 +1,49 @@
+// TC: O(m+ n), where m is the length of s, and n is the length of t
+// SC: O(n)
+
+function minWindow(s: string, t: string): string {
+  const tCnt = new Map<string, number>();
+  const windowCnt = new Map<string, number>();
+
+  for (const ch of t) {
+    tCnt.set(ch, (tCnt.get(ch) || 0) + 1);
+  }
+
+  let left = 0;
+  let validWindowKeySize = 0;
+  let minStrLength = Infinity;
+  let minLeft = 0;
+
+  for (let right = 0; right < s.length; right++) {
+    const ch = s[right];
+
+    windowCnt.set(ch, (windowCnt.get(ch) || 0) + 1);
+
+    if (tCnt.has(ch) && tCnt.get(ch) === windowCnt.get(ch)) {
+      validWindowKeySize++;
+    }
+
+    // When windowCnt's keys include all the keys from tCnt
+    while (tCnt.size === validWindowKeySize && left <= right) {
+      // Update the minimum window details: start index (minLeft) and length (minStrLength)
+      if (right - left + 1 < minStrLength) {
+        minStrLength = right - left + 1;
+        minLeft = left;
+      }
+
+      // shrink the window by moving the left pointer
+      const ch = s[left];
+      windowCnt.set(ch, windowCnt.get(ch)! - 1);
+
+      if (tCnt.has(ch) && windowCnt.get(ch)! < tCnt.get(ch)!) {
+        validWindowKeySize--;
+      }
+
+      left++;
+    }
+  }
+
+  return minStrLength === Infinity
+    ? ""
+    : s.slice(minLeft, minLeft + minStrLength);
+}