go: add «633. Sum of Square Numbers»

Signed-off-by: Matej Focko <me@mfocko.xyz>

go/sum-of-square-numbers.go

@@ -0,0 +1,28 @@
+package main
+
+func judgeSquareSum(c int) bool {
+	bsearch := func(left, right, target int64) bool {
+		for left <= right {
+			mid := left + (right-left)/2
+
+			if mid*mid == target {
+				return true
+			} else if mid*mid > target {
+				right = mid - 1
+			} else {
+				left = mid + 1
+			}
+		}
+
+		return false
+	}
+
+	t := int64(c)
+	for a := int64(0); a*a <= t; a++ {
+		b := t - a*a
+		if bsearch(0, b, b) {
+			return true
+		}
+	}
+	return false
+}