add code of 69

Author: Li Li

top-interview-questions/69. Sqrt(x).cs

@@ -0,0 +1,31 @@
+// Binary search
+public class Solution {
+    public int MySqrt(int x) {
+        if (x == 0) return 0;
+        int left = 1, right = x;
+        while (left + 1 < right) {
+            int mid = left + (right - left) / 2;
+            if (mid == x / mid) {
+                return mid;
+            } else if (mid > x / mid) {
+                right = mid;
+            } else {
+                left = mid;
+            }
+        }
+        if (right <= x / right) return right;
+        return left;
+    }
+}
+
+// NewTon
+public class Solution {
+    public int MySqrt(int x) {
+        if (x == 0) return 0;
+        long r = x;
+        while (r * r > x) {
+            r = (r + x / r) / 2;
+        }
+        return (int)r;
+    }
+}