feat: Added 50 Pow(x,n) for nodejs

- feat: Added using recursion for permuatation problem example in nodejs

.gitignore

@@ -1 +1,2 @@
 /.gtm/
+.vimspector.json

pow-x-n/nodejs/index.js

@@ -0,0 +1,96 @@
+/*
+Implement pow(x, n), which calculates x raised to the power n (xn).
+
+Example 1:
+
+Input: 2.00000, 10
+Output: 1024.00000
+Example 2:
+
+Input: 2.10000, 3
+Output: 9.26100
+Example 3:
+
+Input: 2.00000, -2
+Output: 0.25000
+Explanation: 2-2 = 1/22 = 1/4 = 0.25
+Note:
+
+-100.0 < x < 100.0
+n is a 32-bit signed integer, within the range [−231, 231 − 1]
+*/
+const { assert }  = require('../../util/js'); 
+/**
+ * @param {number} x
+ * @param {number} n
+ * @return {number}
+ */
+var myPow = function(x, n) {
+
+  const isNeg = n < 0 ? true: false;
+  if (n === 0) {
+    return 1;
+  }
+  if (n === 1) {
+    return x;
+  }
+  if (n === -1) {
+    return 1/x;
+  }
+
+  const storedCalcs = {};
+
+  const recursivePow = (x, n) => {
+
+
+    if (n === 2) {
+      return isNeg ? (1/x * 1/x) : x * x;
+    }
+    if (n === 1) {
+      return isNeg ? 1/x : x;
+    }
+    if (n === 0) {
+      return 1;
+    }
+
+    const firstHalf = Math.floor(parseInt(Math.abs(n) / 2));
+    const secondHalf = Math.abs(n) - firstHalf; 
+
+    if(storedCalcs[n]) {
+      return storedCalcs[n];
+    }
+    const result = recursivePow(x, firstHalf) * recursivePow(x, secondHalf);
+    storedCalcs[n] = result;
+    return result;
+
+  };
+
+  return  recursivePow(x, n);
+}
+
+/* Test Case 1
+ * Input: 2.00000, 10
+ * Output: 1024.00000
+ */
+x = 2.00000;
+n = 10;
+sol = 1024.00000;
+assert(myPow(x, n) == sol,  'Output: 1024.00000');
+
+/* Test Case 2
+ * Input: 2.10000, 3
+ * Output: 9.261
+ */
+x = 2.10000;
+n = 3;
+sol = 9.261;
+assert(myPow(x, n).toFixed(3) == sol,  'Output: 9.261');
+
+/* Test Case 3
+ * Input: 2.00000, -2
+ * Output: 0.25
+ */
+x = 2.00000;
+n = -2;
+sol = 0.25;
+assert(myPow(x, n) == sol, 'Output: 0.25000');

rec-permute/nodejs/index.js

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+const RecPermute = (soFar, rest) => {
+  if (rest.length === 0) {
+    console.log('result', soFar);
+    console.log('\n\n');
+  } else {
+    for (let i = 0; i < rest.length; i++) {
+      const remaining = rest.substring(0,i) + rest.substring(i+1);
+      console.log('r', remaining) 
+      console.log('R', rest);
+      console.log('SF', soFar);
+      console.log('------');
+      RecPermute(soFar + rest[i], remaining);
+    }
+  }
+};
+
+x = 'abc';
+RecPermute('', x);