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栈是一种后进先出的数据结构

s.push压栈,s.pop弹出栈顶,s.top获取栈顶元素

栈实现

Stack.hpp
Stack.cpp

函数调用栈

递归与栈

递归函数的实现是基于函数栈实现的

递归可以使用栈来实现,通过栈保存当前环境

单调栈

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函数模板

类模板

模板的非类型参数

bitset_1.h

模板的实例化

隐式实例化

显示实例化

模板的特化

模板的继承

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union


在C/C++程序的编写中,当多个基本数据类型或复合数据结构要占用同一片内存时,我们要使用联合体;当多种类型,多个对象,多个事物只取其一时(我们姑且通俗地称其为“n 选1”),我们也可以使用联合体来发挥其长处。


vector4 用来表示向量和颜色

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struct  vector4
{
union
{
struct {
float r;
float g;
float b;
float a;
};
struct
{
float x;
float y;
float z;
float w;
};
};
};
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void test() {
vector4 v4;
v4.x = 1.0f;
v4.y = 2.0f;
cout << v4.x << " " << v4.y << endl;
cout << v4.r << " " << v4.g << endl;

v4.r = 2.0f;
v4.g = 1.0f;
cout << v4.x << " " << v4.y << endl;
cout << v4.r << " " << v4.g << endl;
}
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1363F Rotating Substrings

问题描述


You are given two strings s and t, each of length n and consisting of lowercase Latin alphabets. You want to make s equal to t.

You can perform the following operation on s any number of times to achieve it —

Choose any substring of s and rotate it clockwise once, that is, if the selected substring is s[l,l+1…r], then it becomes s[r,l,l+1…r−1]. All the remaining characters of s stay in their position.
For example, on rotating the substring [2,4] , string “abcde” becomes “adbce”.

A string a is a substring of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters from the beginning and several (possibly, zero or all) characters from the end.

Find the minimum number of operations required to convert s to t, or determine that it’s impossible.

Input
The first line of the input contains a single integer t (1≤t≤2000) — the number of test cases. The description of the test cases follows.

The first line of each test case contains a single integer n (1≤n≤2000) — the length of the strings.

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