Merge pull request #2 from ignacio-chiazzo/parent

Added Generate Parentheses

Author: ignacio-chiazzo

GenerateParentheses.js

@@ -0,0 +1,96 @@
+/* 
+https://leetcode.com/problems/generate-parentheses
+
+Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
+
+For example, given n = 3, a solution set is:
+
+[
+  "((()))",
+  "(()())",
+  "(())()",
+  "()(())",
+  "()()()"
+]
+*/
+
+// ************************************************  Approach1  ************************************************
+var generateParenthesesApproach1 = function(n) {
+  if(n === 0) { return [] };
+
+  var str = "(".repeat(n);
+    sol = [];
+  
+  genParAux(str, 0, 0, sol)
+  return sol;
+};
+
+/* 
+@param {string} str contains the string generated.
+@param {number} position Current position of the string where new parenthesis would be added.
+@param {string} leftParenthesis Amount for parenthesis left to be added.
+@param {[string]} sol array that contains the solution found so far.
+*/
+
+var genParAux = function(str, position, leftParentheses, sol) {
+  if(position === str.length) {
+    var ret = str + ")".repeat(leftParentheses);
+    sol.push(ret);
+    return;
+  }
+
+  genParAux(str, position + 1, leftParentheses + 1, sol); // Don't insert anything
+  if(leftParentheses === 0) { return; }
+
+  for(var i = 1; i <= leftParentheses; i++) {
+    var parString = ")".repeat(i);
+    var partSol = str.slice(0, position) + parString + str.slice(position); // Insert i parentheses in the position
+    genParAux(partSol, position + i + 1, leftParentheses - i + 1, sol);
+  } 
+}
+
+// ************************************************  Approach2  ************************************************
+var generateParenthesesApproach2 = function(n) {
+  if(n === 0) { return [] };
+
+  var sol = [];
+  genParAuxApproach2("", 0, 0, 0, n * 2, sol)
+  return sol;
+}
+
+var genParAuxApproach2 = function(str, leftPar, rightPar, index, totalCharCount, sol) {
+  if(index === totalCharCount) {
+    if(rightPar === leftPar) {
+      sol.push(str);
+    }
+    return;
+  }
+
+  var strLeft = insertAt(str, index, "(");
+  genParAuxApproach2(strLeft, leftPar + 1, rightPar, index + 1, totalCharCount, sol);
+
+  if(rightPar === leftPar) { return; }
+  
+  var strRight = insertAt(str, index, ")");
+  genParAuxApproach2(strRight, leftPar, rightPar + 1, index + 1, totalCharCount, sol);
+}
+
+var insertAt = function(str, position, value) {
+  return str.slice(0, position) + value + str.slice(position);
+}
+
+function main() {
+  console.log("Approach 1");
+  [0, 1, 2, 3].forEach(function(elem) {
+    console.log(`${elem}: ${generateParenthesesApproach2(elem)}`);
+  })
+
+  console.log("-------------");
+
+  console.log("Approach 2");
+  [0, 1, 2, 3].forEach(function(elem) {
+    console.log(`${elem}: ${generateParenthesesApproach2(elem)}`);
+  })
+}
+main();
+module.exports.main = main

Main.js

@@ -2,6 +2,7 @@
 var permutationWithoutDuplicates = require("./PermutationsWithoutDuplicates.js");
 var permutationWithDuplicates = require("./PermutationsWithDuplicates.js");
 var subsets = require("./Subsets.js");
+var generateParentheses = require("./GenerateParentheses.js")
 var maximunSubarray = require("./MaximunSubarray.js");
 var coinChange = require("./CoinChange.js");
 var nQueens = require("./NQueens.js");
@@ -13,6 +14,7 @@ var floodFill = require("./FloodFill.js")
 // permutationWithoutDuplicates.main();
 // permutationWithDuplicates.main();
 // subsets.main();
+// generateParentheses.main();
 // maximunSubarray.main();
 // coinChange.main();
 // nQueens.main();