69.sqrt-x.java

/*
 * @lc app=leetcode id=69 lang=java
 *
 * [69] Sqrt(x)
 *
 * https://leetcode.com/problems/sqrtx/description/
 *
 * algorithms
 * Easy (31.96%)
 * Likes:    870
 * Dislikes: 1497
 * Total Accepted:    410.5K
 * Total Submissions: 1.3M
 * Testcase Example:  '4'
 *
 * Implement int sqrt(int x).
 *
 * Compute and return the square root of x, where x is guaranteed to be a
 * non-negative integer.
 *
 * Since the return type is an integer, the decimal digits are truncated and
 * only the integer part of the result is returned.
 *
 * Example 1:
 *
 *
 * Input: 4
 * Output: 2
 *
 *
 * Example 2:
 *
 *
 * Input: 8
 * Output: 2
 * Explanation: The square root of 8 is 2.82842..., and since
 * the decimal part is truncated, 2 is returned.
 *
 *
 */
class Solution {
  public int mySqrt(int x) {
    int low = 1;
    int high = x;
    while (low <= high) {
      int mid = low + (high - low) / 2;
      if (mid == x / mid) {
        return mid;
      } else if (mid > x / mid) {
        high = mid - 1;
      } else {
        low = mid + 1;
      }
    }
    return high;
  }
}