[nb] Commit

dynamic-programming/22-generate-parenthesis/golang/main.go

@@ -1,4 +1,8 @@
 package main
+import (
+  "strings"
+  "container/list"
+)
 /*
 Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
 Example 1:
@@ -20,37 +24,30 @@ Constraints:
 1 <= n <= 8
 */
 
-func rec(int index, dp map[string]string) {
+func rec(input []string, left int, right int, n int, ans *[]string) {
+
+  if len(input) == 2*n {
+    *ans = append(*ans, strings.Join(input, ""))
+    return
+  }
+  if left < n {
+    input = append(input, "(")
+    rec(input, left+1, right, n, ans)
+    input = input[0:len(input)-1]
+  }
+  if right < left {
+    input = append(input, ")")
+    rec(input, left, right+1, n, ans)
+    input = input[0:len(input)-1]
+  }
 }
 
-
-func generateParenthesis(n int)[] string {
-
-  if n == 1 {
-    return []string{"()"}
-  }
-
-  if n == 2 {
-    return []string{"()()", "(())"}
-  }
-
-  var output = make([]string, 0) 
-  var dp = map[string]string{}
-  var start_string string = ""
-  for i := 0; i < n - 1; i++ {
-    start_string = start_string + "()"
-    out_arr = a
-  }
-  output = append(output, start_string)
-
-
-  for i := 1; i < n - 1; i++ {
-    result := rec(i+1, dp) + rec(i-1) 
-  }
-
-
+func generateParenthesis(n int) []string {
+  var output = make([]string, 2*n)
+  var input = make([]string, 2*n)
+  rec(input, 0, 0, n, &output)
+  return output
 }
-
 func main() {
-
+  generateParenthesis(3)
 }

dynamic-programming/22-generate-parenthesis/js/index.js

@@ -1,17 +1,30 @@
 function generateParenthesis(n) {
-  if (n == 1) {
-    return ['()'];
+  const output = []
+  const rec = (input = [], left = 0, right = 0) => {
+    if (input.length === 2*n) {
+      output.push(input.join(''));
+      console.log('sol');
+      return
+    }
+    if (left < n) {
+      input.push('(');
+      console.log(input.join('') + ' l=' + left + ' r=' + right)
+      rec(input, left+1, right);
+      console.log('back left');
+      input.pop();
     }
 
-  if (n == 2) {
-    return ['()()', '(())'];
-  }
-
-  const input = [];
-  for (i = 0; i < n; i++) {
-    input.push('()');
-  }
-
-  for(i = 0; i < n; i++; i++) {
+    if (right < left) {
+      input.push(')');
+      console.log(input.join('') + ' l=' + left + ' r=' + right)
+      rec(input, left, right+1);
+      console.log('back right l=' + left);
+      input.pop();
+      console.log(input.join('') + ' l=' + left + ' r=' + right)
     }
+  };
+  rec();
+  return output;
 }
+
+console.log(generateParenthesis(3));

dynamic-programming/22-generate-parenthesis/python/index.py

@@ -0,0 +1,25 @@
+from typing import List
+# ()()()
+# (())()
+# ((()))
+# ()(())
+# (()())
+
+def generateParenthesis(n: int) -> List[str]:
+    ans = []
+    def backtrack(S = [], left = 0, right = 0):
+        if len(S) == 2 * n:
+            ans.append("".join(S))
+            return
+        if left < n:
+            S.append("(")
+            backtrack(S, left+1, right)
+            S.pop()
+        if right < left:
+            S.append(")")
+            backtrack(S, left, right+1)
+            S.pop()
+    backtrack()
+    return ans
+
+generateParenthesis(3)