add link to Minimum Window Substring

Author: fishercoder1534

HARD/src/hard/MinimumWindowSubstring.java

@@ -0,0 +1,36 @@
+package hard;
+
+/**
+ * Created by fishercoder1534 on 10/3/16.
+ */
+public class MinimumWindowSubstring {
+
+    public String minWindow(String s, String t) {
+        int[] counts = new int[256];
+        for(char c : t.toCharArray()){
+            counts[c]++;
+        }
+
+        int start = 0, end = 0, minStart = 0, minLen = Integer.MAX_VALUE, counter = t.length();
+        while(end < s.length()){
+            if(counts[s.charAt(end)] > 0) counter--;
+
+            counts[s.charAt(end)]--;
+            end++;
+
+            while(counter == 0){
+                if(end-start < minLen){
+                    minStart = start;
+                    minLen = end-start;
+                }
+                counts[s.charAt(start)]++;
+                if(counts[s.charAt(start)] > 0) counter++;
+                start++;
+            }
+        }
+
+        if(minLen == Integer.MAX_VALUE) return "";
+        return s.substring(minStart, minStart+minLen);
+    }
+
+}

README.md

@@ -4,6 +4,7 @@
 |278|[First Bad Version](https://leetcode.com/problems/first-bad-version/)|[Solution](../../blob/master/EASY/src/easy/FirstBadVersion.java)| O(logn)|O(1) | Easy| Binary Search
 |133|[Clone Graph](https://leetcode.com/problems/clone-graph/)|[Solution](../../blob/master/MEDIUM/src/medium/CloneGraph.java)| O(n)|O(n) | Medium| HashMap, BFS 
 |91|[Decode Ways](https://leetcode.com/problems/decode-ways/)|[Solution](../../blob/master/MEDIUM/src/medium/DecodeWays.java)| O(n)|O(n) | Medium| DP
+|76|[Minimum Window Substring](https://leetcode.com/problems/minimum-window-substring/)|[Solution](../../blob/master/HARD/src/hard/MinimumWindowSubstring.java)|O(n)|O(k)|Hard|Two Pointers
 |23|[Merge k Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/)|[Solution](../../blob/master/HARD/src/hard/MergeKSortedList.java)|O(n*logk)|O(logk)|Hard|Heap
 |17|[Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/)|[Solution](../../blob/master/MEDIUM/src/medium/LetterCombinationsofaPhoneNumber.java)|O(n*4^n)|O(n)|Medium|Backtracking
 |10|[Regular Expression Matching](https://leetcode.com/problems/regular-expression-matching/)|[Solution](../../blob/master/HARD/src/hard/RegularExpressionMatching.java)|O(m*n)|O(m*n)|Hard|DP