Create 1531-string-compression-ii.js

aadil42 · web-flow · commit 2b97001308cc · 2025-03-28T15:42:43.000+05:30
Add Brute force solution. Add memoization solution.
diff --git a/javascript/1531-string-compression-ii.js b/javascript/1531-string-compression-ii.js
@@ -0,0 +1,92 @@
+/**
+ * DP | Recursion | Memoization
+ * Time O(n^4) | Space O(n^4)
+ * https://leetcode.com/problems/string-compression-ii/
+ * @param {string} s
+ * @param {number} k
+ * @return {number}
+ */
+function getLengthOfOptimalCompression(s, k) {
+    const cache = new Map();
+
+    const dfs = (i, pre, freqOfSameChar, leftK) => {
+
+        const hash = `${i},${pre},${freqOfSameChar},${leftK}`;
+        if (cache.has(hash)) return cache.get(hash);
+
+        if (leftK < 0) return Infinity;
+        if (i === s.length) return 0;
+
+        const deleteChar = dfs(i+1, pre, freqOfSameChar, leftK-1);
+
+        let keepChar;
+
+        if (s[i] === pre) {
+
+            const addOneOrZero = (freqOfSameChar === 1 || freqOfSameChar === 9 || freqOfSameChar === 99) ? 1 : 0;
+            keepChar = addOneOrZero + dfs(i+1, pre, freqOfSameChar + 1, leftK);
+        } else {
+
+            keepChar = 1 + dfs(i+1, s[i], 1, leftK);
+        }
+
+        cache.set(hash, Math.min(deleteChar, keepChar));
+
+        return cache.get(hash);
+    }
+
+    return dfs(0, -1, 0, k);
+}
+
+
+/**
+ * Brute force.
+ * Time O(2^n) | Space O(n)
+ * https://leetcode.com/problems/string-compression-ii
+ * @param {string} s
+ * @param {number} k
+ * @return {number}
+ */
+var getLengthOfOptimalCompressionBF = function(s, k) {
+    
+    const runLengthEncoded = (str) => {
+        const encodedStr = [];
+        let left = 0;
+        let right = 1;
+
+        while(right < str.length + 1) {
+            while(str[left] === str[right]) {
+                right++;
+            }
+            const len = right - left;
+            if(len > 1) {
+                encodedStr.push(str[left], len);
+            } else {
+                encodedStr.push(str[left])
+            }
+            
+            left = right;
+            right++;
+        }
+
+        return encodedStr.join("").length;
+    }
+
+    let min = Infinity;
+    const dfs = (i, str, deleteLeft) => {
+        // console.log(str)
+        const hash = `${i}-${deleteLeft}`;
+        
+        if(i === s.length) {
+            min = Math.min(min, runLengthEncoded(str))
+            return;
+        }
+        if(deleteLeft > 0) {
+            return Math.min(dfs(i+1, str+s[i], deleteLeft), dfs(i+1, str, deleteLeft-1));
+        }
+        return dfs(i+1, str+s[i], deleteLeft);
+    }
+
+    dfs(0, "", k);
+    return min;
+};
