diff --git a/budd-common/src/main/java/io/github/ehlxr/algorithm/MinWindow.java b/budd-common/src/main/java/io/github/ehlxr/algorithm/MinWindow.java
new file mode 100644
index 0000000..4129e7c
--- /dev/null
+++ b/budd-common/src/main/java/io/github/ehlxr/algorithm/MinWindow.java
@@ -0,0 +1,86 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright © 2022 xrv <xrv@live.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package io.github.ehlxr.algorithm;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * @author ehlxr
+ * @since 2022-04-29 11:07.
+ */
+public class MinWindow {
+    public static void main(String[] args) {
+        System.out.println(minWindow("cabwefgewcwaefgcf", "cae"));
+        System.out.println(minWindow("bba", "ab"));
+        System.out.println(minWindow("ADOBECODEBANC", "ABC"));
+        System.out.println(minWindow("a", "a"));
+        System.out.println(minWindow("a", "b"));
+        System.out.println(minWindow("", "a"));
+        System.out.println(minWindow("", ""));
+        System.out.println(minWindow("a", "aa"));
+        System.out.println(minWindow("aa", "a"));
+    }
+
+    public static String minWindow(String s, String t) {
+        Map<Character, Integer> windows = new HashMap<>();
+        Map<Character, Integer> needs = new HashMap<>();
+        for (int i = 0; i < t.length(); i++) {
+            needs.put(t.charAt(i), needs.getOrDefault(t.charAt(i), 0) + 1);
+        }
+
+        int left = 0, right = 0, valid = 0, start = -1, len = Integer.MAX_VALUE;
+        while (right < s.length()) {
+            char r = s.charAt(right);
+
+            if (needs.containsKey(r)) {
+                windows.put(r, windows.getOrDefault(r, 0) + 1);
+                if (windows.get(r).equals(needs.get(r))) {
+                    valid++;
+                }
+            }
+            right++;
+
+            while (valid == needs.size()) {
+                if (right - left < len) {
+                    len = right - left;
+                    start = left;
+                }
+
+                char l = s.charAt(left);
+                left++;
+
+                if (windows.containsKey(l)) {
+                    if (windows.get(l).equals(needs.get(l))) {
+                        valid--;
+                    }
+                    windows.put(l, windows.get(l) - 1);
+                }
+            }
+        }
+
+        return start > -1 ? s.substring(start, start + len) : "";
+    }
+}