206: Concealed square

206_concealed_square/main.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"math/big"
+)
+
+func main() {
+	solution()
+}
+
+func solution() {
+	n := math.Sqrt(19293949596979899)
+	t := math.Sqrt(10203040506070809)
+	for i := n; i >= t; i-- {
+		if i == 1389019170 {
+			fmt.Println(i)
+		}
+		x := (&big.Int{}).SetInt64(int64(i))
+		if isMatch(x.Mul(x, x)) {
+			fmt.Println(x)
+			fmt.Println("num is", int64(i)*10)
+		}
+	}
+}
+
+func isMatch(i *big.Int) bool {
+	x := i.String()
+	num := x[0]
+	for i := 2; i < len(x); i += 2 {
+		if x[i] == num+1 {
+			num++
+			continue
+		}
+		return false
+	}
+	return true
+}