Feat | NeetCode | Roadmap | #19 Minimum Window Substring

README.md

@@ -89,4 +89,5 @@
   - [Task #15](src/neetcode/sliding-window/best-time-to-buy-and-sell-stock) – _Best Time To Buy And Sell Stock_ - _[check the task](https://neetcode.io/problems/buy-and-sell-crypto)_
   - [Task #16](src/neetcode/sliding-window/longest-substring-without-repeating-characters) – _Longest Substring Without Repeating Characters_ - _[check the task](https://neetcode.io/problems/longest-substring-without-duplicates)_
   - [Task #17](src/neetcode/sliding-window/longest-repeating-character-replacement) – _Longest Repeating Character Replacement_ - _[check the task](https://neetcode.io/problems/longest-repeating-substring-with-replacement)_
-  - [Task #18](src/neetcode/sliding-window/permutation-in-string) – _Permutation In String_ - _[check the task](https://neetcode.io/problems/permutation-string)_
+  - [Task #17](src/neetcode/sliding-window/longest-repeating-character-replacement) – _Longest Repeating Character Replacement_ - _[check the task](https://neetcode.io/problems/longest-repeating-substring-with-replacement)_
+  - [Task #19](src/neetcode/sliding-window/minimum-window-substring) – _Minimum Window Substring_ - _[check the task](https://neetcode.io/problems/minimum-window-with-characters)_

src/neetcode/sliding-window/minimum-window-substring/solution.test.ts

@@ -0,0 +1,27 @@
+import { minWindow } from './solution';
+
+describe('Minimum Window Substring | NeetCode | RoadMap | Testcases', () => {
+  test('#1 Substring containing t characters', () => {
+    const s = 'OUZODYXAZV';
+    const t = 'XYZ';
+    const expected = 'YXAZ';
+    const output = minWindow(s, t);
+    expect(output).toBe(expected);
+  });
+
+  test('#2 Exact t string', () => {
+    const s = 'xyz';
+    const t = 'xyz';
+    const expected = 'xyz';
+    const output = minWindow(s, t);
+    expect(output).toBe(expected);
+  });
+
+  test('#3 No such substring', () => {
+    const s = 'x';
+    const t = 'xy';
+    const expected = '';
+    const output = minWindow(s, t);
+    expect(output).toBe(expected);
+  });
+});

src/neetcode/sliding-window/minimum-window-substring/solution.ts

@@ -0,0 +1,49 @@
+/**
+ * @param {string} s - first string
+ * @param {string} t - second string
+ * @return {string} the shortest substring of `s` such that every character in `t`, including duplicates,
+ * is present in the substring. If such a substring does not exist, an empty string `""` will be returned.
+ */
+export const minWindow = (s: string, t: string): string => {
+  if (t.length > s.length) {
+    return '';
+  }
+
+  let mxLen = Infinity;
+  let fulfilled = 0;
+
+  const tChars: Record<string, number | undefined> = {};
+  const sChars: Record<string, number | undefined> = {};
+  const resIdx = [-1, -1];
+
+  for (const ch of t) {
+    tChars[ch] = (tChars[ch] ?? 0) + 1;
+  }
+
+  const need = Object.keys(tChars).length;
+  let l = 0;
+
+  for (let r = 0; r < s.length; r++) {
+    sChars[s[r]] = (sChars[s[r]] ?? 0) + 1;
+
+    if (sChars[s[r]] === tChars[s[r]]) {
+      fulfilled++;
+    }
+
+    while (fulfilled === need) {
+      if (r - l + 1 < mxLen) {
+        mxLen = r - l + 1;
+        resIdx[0] = l;
+        resIdx[1] = r + 1;
+      }
+
+      sChars[s[l]] = (sChars[s[l]] ?? 0) - 1;
+      if ((sChars[s[l]] ?? 0) < (tChars[s[l]] ?? 0)) {
+        fulfilled--;
+      }
+      l++;
+    }
+  }
+
+  return mxLen === Infinity ? '' : s.slice(resIdx[0], resIdx[1]);
+};