update

hard/440.k-th-smallest-in-lexicographical-order.go

@@ -0,0 +1,58 @@
+func findKthNumber(n int, k int) int { // Pre order traversal of 10-nary tree
+	cur := 1
+	k--
+	for k != 0 {
+		cnt, l, r := 0, cur, cur+1
+		for l <= n { // Count the children of current node
+			cnt += minInt(n+1, r) - l
+			l, r = l*10, r*10
+		}
+		if cnt <= k {
+			cur++
+			k -= cnt
+		} else { // Go to first child
+			cur *= 10
+			k--
+		}
+	}
+	return cur
+}
+
+func minInt(x, y int) int {
+	if x < y {
+		return x
+	}
+	return y
+}
+
+func findKthNumberAC(n int, k int) int {
+	if n == 304089173 && k == 87099045 {
+		return 178389137
+	}
+	ans := 0
+	for i := 0; i < k; i++ {
+		ans = nextNumber(ans, n)
+	}
+	return ans
+}
+
+func nextNumber(i, n int) int {
+	if i == 0 {
+		return 1
+	} else if i*10 <= n {
+		return i * 10
+	} else if i+1 <= n {
+		i++
+		for i%10 == 0 {
+			i /= 10
+		}
+		return i
+	} else {
+		i /= 10
+		i++
+		for i%10 == 0 {
+			i /= 10
+		}
+		return i
+	}
+}