Valid Perfect Square
Given a positive integer num, write a function which returns True if num is a perfect square else False.
Note: Do not use any built-in library function such as sqrt.
Example 1:
Input: 16
Output: true
Example 2:
Input: 14
Output: false
Solution
/**
* @param {number} num
* @return {boolean}
* @time complexity: O(log n)
* @space complexity: O(1)
*/
function isValidPerfectSquare(num) {
// Binary Search
let left = 0;
let right = num;
while (left <= right) {
const mid = Math.floor((left + right) / 2);
const tmp = mid * mid;
if (tmp === num) {
return true;
}
if (tmp > num) {
right = mid - 1;
} else {
left = mid + 1;
}
}
return false;
};
Test Case
const assert = require('chai').assert;
describe('Valid Perfect Square', () => {
it('should return true when 16 is given', () => {
assert.deepEqual(isValidPerfectSquare(16), true);
});
it('should return false when 14 is given', () => {
assert.deepEqual(isValidPerfectSquare(14), false);
});
});
Valid Perfect Square
✓ should return true when 16 is given
✓ should return false when 14 is given
2 passing (17ms)
