sqrt(x) Problem & Solution

Given a non-negative integer x, compute and return the square root of x. Since the return type is an integer, the decimal digits are truncated, and only the integer part of the result is returned.

See the sqrt(x) problem on LeetCode.

C++ Solution

#pragma GCC optimize("Ofast")
#pragma GCC optimization("unroll-loops")

static const int _=[](){std::ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();

class Solution {
public:
  int mySqrt(int x) {
    int low = 0;
    int high = x;
    while (low < high) {
      int mid = low + (high - low) / 2;

      // Avoid overflow when computing `mid * mid < x`.
      if (mid == 0 || mid < x / mid) {
        low = mid + 1;
      } else {
        high = mid;
      }
    }

    // Avoids overflow when computing `low * low > x`.
    return low != 0 && low > x / low ? low - 1 : low;
  }
};

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