97 lines
1.6 KiB
JavaScript
97 lines
1.6 KiB
JavaScript
|
/*
|
|||
|
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');
|