add: 230927

cpp/2308/LC230927.cpp

@@ -0,0 +1,37 @@
+#include <cctype>
+#include <string>
+#include <vector>
+#include <tuple>
+
+#include "defs.h"
+
+std::string LC230927::decodeAtIndex(const std::string& s, int k) {
+	std::vector<std::tuple<std::string, int, unsigned long long>> col;
+	unsigned long long len = 0;
+	std::string buf;
+	for (char ch : s) {
+		if (std::isalpha(ch)) {
+			++len;
+			buf += ch;
+		} else { // num
+			col.emplace_back(buf, ch ^ 0x30, len *= (ch ^ 0x30));
+			buf.clear();
+		}
+		if (len >= k)
+			break;
+	}
+	if (!buf.empty())
+		col.emplace_back(buf, 1, len);
+	const int level = col.size();
+	int ck = k - 1;
+	for (int i = level - 1; i >= 0; --i) {
+		const auto prev_len = i ? std::get<2>(col[i - 1]) : 0ULL;
+		const auto& [c_str, c_dup, cur_len] = col[i];
+		ck %= (cur_len / c_dup);
+		if (ck >= prev_len)
+			return {c_str[ck - prev_len]};
+	}
+	return {std::get<0>(col[0])[ck]};
+}
+
+

cpp/2308/defs.h

@@ -26,4 +26,9 @@ public:
 	static int bestClosingTime(const std::string&);
 };
 
+class LC230927 {
+public:
+	static std::string decodeAtIndex(const std::string& s, int k);
+};
+
 #endif //LEETCODE_CPP_DEFS_H

cpp/2308/main.cpp

@@ -2,7 +2,6 @@
 #include <iostream>
 
 int main() {
-	LC230827 s;
-	std::cout << s.canCross({0,1,3,5,6,8,12,17});
+	std::cout << LC230927::decodeAtIndex("a2b3c4d5e6f7g8h9", 9);
 	return 0;
 }