Create 2116-check-if-a-parentheses-string-can-be-valid.js

javascript/2116-check-if-a-parentheses-string-can-be-valid.js

@@ -0,0 +1,115 @@
+/**
+ * Stack | Greedy
+ * Time O(n) | Space O(n)
+ * https://leetcode.com/problems/check-if-a-parentheses-string-can-be-valid
+ * @param {string} s
+ * @param {string} locked
+ * @return {boolean}
+ */
+var canBeValid = function(s, locked) {
+
+    const unlockedStack = [];
+    const lockedStack = [];
+
+    for (let i = 0; i < s.length; i++) {
+
+        if (locked[i] === "0") {
+            unlockedStack.push(i);
+            continue;
+        }
+
+        if (s[i] === "(") {
+            lockedStack.push(i);
+            continue;
+        }
+
+        if (s[i] === ")") {
+
+            if (lockedStack.length) {
+                lockedStack.pop();
+                continue;
+            }
+
+            if (unlockedStack.length) {
+                unlockedStack.pop();
+                continue;
+            } 
+
+            return false;
+        }
+    }
+
+    while (lockedStack.length && 
+           unlockedStack.length && 
+           lockedStack[lockedStack.length - 1] < unlockedStack[unlockedStack.length - 1]) {
+            lockedStack.pop();
+            unlockedStack.pop();
+    }
+
+    return unlockedStack.length % 2 === 0 && lockedStack.length === 0;
+};
+
+/**
+ * Brute Force | Recursion | BackTracking
+ * Time (2^n * n) | Space O(n)
+ * https://leetcode.com/problems/check-if-a-parentheses-string-can-be-valid
+ * @param {string} s
+ * @param {string} locked
+ * @return {boolean}
+ */
+var canBeValidBF = function(s, locked) {
+
+    if (!s.length) return false;
+    if (s[0] === ")" && locked[0] === "1") return false;
+    if (s[s.length - 1] === "(" && locked[locked.length - 1] === "1") return false;
+
+    const dfs = (idx, arr) => {
+
+        if (idx === s.length && isValid(arr)) return true;
+        if (idx === s.length) return false;
+
+        // we have two choices. either change it or not change it.
+        if (locked[idx] === "0") {
+            arr.push("(");
+            const choice1 = dfs(idx+1, arr);
+            arr.pop();
+
+            if (choice1) return choice1;
+
+            arr.push(")");
+            const choice2 = dfs(idx+1, arr);
+            arr.pop();
+
+            return choice2;
+        }
+
+        // we only have once choice.
+        if (s[idx] === "(") {
+            arr.push("(");
+            const val = dfs(idx+1, arr);
+            arr.pop();
+            return val;
+        }
+
+        if (s[idx] === ")") {
+            arr.push(")");
+            const val = dfs(idx+1, arr);   
+            arr.pop();
+            return val;         
+        }
+    }
+
+    return dfs(0, []);
+};
+
+const isValid = (arr) => {
+
+    let balancer = 0;
+
+    for (let i = 0; i < arr.length; i++) {
+        if (arr[i] === "(") balancer++;
+        if (arr[i] === ")") balancer--;
+    }
+
+    return balancer === 0;
+}