Create 0069-sqrt(x).cpp

cpp/0069-sqrt(x).cpp

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+/*
+ 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.
+
+ Ex. Input: x = 4
+ Output: 2
+ Explanation: The square root of 4 is 2, so we return 2.
+
+ Time : O(log N)
+ Space : O(1)
+*/
+
+class Solution {
+public:
+ int mySqrt(int x) {
+ if(x == 0 || x == 1)
+ return x;
+
+ long long beg = 0, mid = 0, end = x/2;
+ while(beg <= end) {
+ mid = (beg + end)/2;
+ if(mid * mid < x) {
+ if((mid + 1) * (mid + 1) > x)
+ return mid;
+ beg = mid+1;
+ } else if(mid * mid > x) {
+ if( (mid - 1) * (mid - 1) < x)
+ return mid-1;
+ end = mid - 1;
+ } else 
+ return mid;
+ }
+ return mid;
+ }
+};