Add minimum window string solution

Author: sudheerj

src/java1/algorithms/strings/MinWindowSubstring.java

@@ -0,0 +1,54 @@
+package java1.algorithms.strings;
+// Sliding window: TC: O(m) + O(n) SC: O(m) + O(n)
+
+import java.util.HashMap;
+
+public class MinWindowSubstring {
+    private static String minWindowSubstring(String windowStr, String subStr) {
+        HashMap<Character, Integer> subStrCount = new HashMap<>();
+        HashMap<Character, Integer> windowStrCount = new HashMap<>();
+
+        int minLength = Integer.MAX_VALUE;
+        int leftIndex = -1, rightIndex = -1;
+
+        for(int i=0; i< subStr.length(); i++) {
+            char ch = subStr.charAt(i);
+            subStrCount.put(ch, subStrCount.getOrDefault(ch, 0) + 1);
+        }
+
+        int having = 0, required = subStrCount.size();
+        int left = 0;
+        for(int right = 0; right < windowStr.length(); right++) {
+            char rightChar = windowStr.charAt(right);
+            windowStrCount.put(rightChar, windowStrCount.getOrDefault(rightChar, 0) + 1);
+            if(subStrCount.containsKey(rightChar) && subStrCount.get(rightChar).intValue() == windowStrCount.get(rightChar).intValue()) {
+                having++;
+            }
+
+            while(required == having) {
+                if(minLength > right-left+1) {
+                    minLength = right-left+1;
+                    leftIndex = left;
+                    rightIndex = right;
+                }
+                char leftChar = windowStr.charAt(left);
+                windowStrCount.put(leftChar, windowStrCount.get(leftChar)-1);
+                if(subStrCount.containsKey(leftChar) && subStrCount.get(leftChar).intValue() > windowStrCount.get(leftChar).intValue()) {
+                    having--;
+                }
+                left++;
+            }
+        }
+        if(leftIndex == -1 || rightIndex == -1) {
+            return "";
+        } else {
+            return windowStr.substring(leftIndex, rightIndex+1);
+        }
+
+    }
+
+    public static void main(String[] args) {
+        String s ="ADOBECODEBANC", t= "ABC";
+        System.out.println(minWindowSubstring(s, t));
+    }
+}

src/javascript/algorithms/strings/minWindowSubstring.js

@@ -0,0 +1,49 @@
+// Sliding window: TC: O(m) + O(n) SC: O(m) + O(n)
+
+function minWindowSubstring(windowStr, subStr) {
+    let windowStrCount = new Map();
+    let subStrCount = new Map();
+
+    let minLength = Number.MAX_VALUE;
+    let leftIndex = rightIndex = -1;
+
+    for(const ch of subStr) {
+        subStrCount.set(ch, (subStrCount.get(ch) || 0) + 1);
+    }
+
+    let having = 0; required = subStrCount.size;
+    let left = right = 0;
+
+    for(right = 0; right < windowStr.length; right++) {
+        let rightChar = windowStr.charAt(right);
+        windowStrCount.set(rightChar, (windowStrCount.get(right) || 0) +1);
+        if(subStrCount.has(rightChar) && subStrCount.get(rightChar) === windowStrCount.get(rightChar)) {
+            having++;
+        }
+
+        while(required === having) {
+            if(minLength > right-left+1) {
+                minLength = right-left+1;
+                leftIndex = left;
+                rightIndex = right;
+            }
+
+            let leftChar = windowStr.charAt(left);
+            windowStrCount.set(leftChar, windowStrCount.get(leftChar)-1);
+            if(subStrCount.has(leftChar) && subStrCount.get(leftChar) > windowStrCount.get(leftChar)) {
+                having--;
+            }
+            left++;
+        }
+    }
+    if(leftIndex === -1 || rightIndex === -1) {
+        return "";
+    } else {
+        return windowStr.substring(leftIndex, rightIndex+1);
+    }
+
+}
+
+let s ="ADOBECODEBANC";
+let t= "ABC";
+console.log(minWindowSubstring(s, t));