add new solutions

solutions/0/q69/solution.go

@@ -0,0 +1,26 @@
+package q69
+
+func mySqrt(x int) int {
+	if x < 2 {
+		return x
+	}
+	l, r := 0, x/2+1
+	for l < r {
+		m := (l + r) / 2
+		sq := m * m
+		switch {
+		case sq == x:
+			return m
+		case sq < x:
+			if (m+1)*(m+1) > x {
+				return m
+			}
+			l = m + 1
+		case sq > x:
+			r = m
+		}
+	}
+	return -1
+}
+
+var _ = mySqrt