add new solutions

solutions/15/q1545/solution.go

@@ -0,0 +1,30 @@
+// Package q1545 implements a solution for https://leetcode.com/problems/find-kth-bit-in-nth-binary-string/
+package q1545
+
+var buf = make([]byte, 1<<20)
+var bufLen = 1
+
+func init() { buf[0] = '0' }
+
+func generate() {
+	buf[bufLen] = '1'
+	newTail := bufLen * 2
+	for i := range bufLen {
+		switch buf[i] {
+		case '0':
+			buf[newTail-i] = '1'
+		case '1':
+			buf[newTail-i] = '0'
+		}
+	}
+	bufLen = newTail + 1
+}
+
+func findKthBit(n, k int) byte {
+	for bufLen < k {
+		generate()
+	}
+	return buf[k-1]
+}
+
+var _ = findKthBit