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69.sqrtx.cpp
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64 lines (56 loc) · 1.27 KB
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// Tag: Math, Binary Search
// Time: N(logN)
// Space: O(1)
// Ref: -
// Note: -
// Given a non-negative integer x, return the square root of x rounded down to the nearest integer. The returned integer should be non-negative as well.
// You must not use any built-in exponent function or operator.
//
// For example, do not use pow(x, 0.5) in c++ or x ** 0.5 in python.
//
//
// Example 1:
//
// Input: x = 4
// Output: 2
// Explanation: The square root of 4 is 2, so we return 2.
//
// Example 2:
//
// Input: x = 8
// Output: 2
// Explanation: The square root of 8 is 2.82842..., and since we round it down to the nearest integer, 2 is returned.
//
//
// Constraints:
//
// 0 <= x <= 231 - 1
//
//
class Solution {
public:
int mySqrt(int x) {
long start = 0;
long end = x;
while (start < end) {
int mid = start + (end - start + 1) / 2;
int sqrt = x / mid;
if (mid > sqrt) {
end = mid - 1;
} else {
start = mid;
}
}
return start;
}
};
class Solution {
public:
int mySqrt(int t) {
long long x = t;
while (x * x > t) {
x = (x + t / x) / 2;
}
return x;
}
};