quiz4: 完成了第一版，修复了忘记自减的问题

quiz4/quiz4.cpp

@@ -0,0 +1,88 @@
+#include <iostream>
+#include <cstring>
+#include <limits.h>
+
+struct node {
+	int id;
+	node* next;
+	node* prev;
+};
+
+void insert_one (node* first, node* curr) {
+	node* insertion_prev = (*first).prev;
+	node* insertion_next = first;
+	(*insertion_next).prev = curr;
+	(*insertion_prev).next = curr;
+	(*curr).next = insertion_next;
+	(*curr).prev = insertion_prev;
+}
+
+void remove_one (node* removal) {
+	node* removal_prev = (*removal).prev;
+	node* removal_next = (*removal).next;
+	(*removal_next).prev = removal_prev;
+	(*removal_prev).next = removal_next;
+	delete removal;
+}
+
+int main () {
+	
+	int n = 0;
+	while (n == 0) {
+		std::string input;
+		int input_n;
+		std::cout << "请输入小人个数: ";
+		std::cin >> input;
+		try {
+			input_n = stoi(input);
+			if (input_n < 1) throw std::exception();
+		} catch (std::out_of_range) {
+			std::cout << "你输入的数字 \"" << input << "\" 太大了，它最大只能是 " << INT_MAX << std::endl;
+			continue;
+		} catch (std::exception) {
+			std::cout << "你的输入是 \"" << input << "\", 但小人的数量必须是一个大于 0 的整数！" << std::endl;
+			continue;
+		}
+		std::cout << "小人个数为 " << input_n << " ? [y/n]";
+		std::cin >> input;
+		if (input == "y")
+			n = input_n;
+	}
+	
+	node* first = new node;
+	(*first).id = 0;
+	(*first).prev = first;
+	(*first).next = first;
+	int count = 1;
+	
+	for (int i = 2; i <= n; i++) {
+		node* curr = new node;
+		(*curr).id = i;
+		insert_one(first, curr);
+		count++;
+	}
+	
+	int counting = 0;
+	node* next_one = (*first).prev;
+	while (count > 1) {
+		node* current = next_one;
+		next_one = (*next_one).next;
+		counting++;
+		std::cout << "小人 #" << (*current).id << "数到了" << counting;
+		if (counting == 3) {
+			remove_one(current);
+			counting = 0;
+			count--;
+			std::cout << " , 出列！还剩下 " << count << "个小人。";
+		} else {
+			std::cout << " .";
+		}
+		std::cout << std::endl;
+	}
+	
+	std::cout << "=====" << std::endl
+			<< "最终剩下了小人 #" << (*first).id << " !" << std::endl;
+	
+	return 0;
+	
+}