[nb] Sync

exercises/pow-x-n/nodejs/index.js

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+/*
+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');