A topic of map

最近学到了map,为了熟悉使用,Find a topic to practice my hand,Topic for cow from：KY264 单词识别

做题链接：单词识别_牛客题霸_牛客网 (nowcoder.com)

目录

题目：

要求：

样例：

思路

代码实现

To realize the dictionary order：

Implementation according to the number to the descending order of

---

题目：

要求：

1. Will sentence the words according to occurrences descending order

2. The same number of words,按照字典序排列（升序排列）

3. 不区分大小写

4. To recognize words and an end

5. Enter a word and a period,Don't consider other symbols

样例：

The sample is worth we noticed is：

开头的大写字母 A ,When the output is in accordance with lowercase letters to

So when we are in the output will be subject to lower case----大写改小写

思路

1. To replace a word in all capital letters with lower case letters

2. 将每个单词插入到map对象中,完成计数+字典序（默认为升序）,符合要求

3. In times aspair类型中的 key 值,单词作为 value 值,插入到 multimap 对象中,Complete the descending order

代码实现

#include<iostream>
#include<string>
#include<map>
using namespace std;
int main()
{
	string str;
	map<string, int> mp;
	while (getline(cin, str))
	{
		int slow = 0;   //Words starting subscript
		string s;       //存放单个单词
		for (int i = 0; i < str.size(); i++)
		{
			//大写变小写
			if ('A' <= str[i] && str[i] <= 'Z')
			{
				str[i] += 32;
			}
			//Take the word into themp中,插入+计数+Automatic descending order
			if (str[i] == ' ' || str[i] == '.')
			{
				int num = i - slow;     //The word size
				s = str.substr(slow, num);  //Through the word starting subscript out and size
				mp[s]++;
				slow = i + 1;  //Skip Spaces to the starting position of the next word
			}
		}

		//The above has been dictionary sequence arranged in a row---The following will be the large number of in front
		//Note number appear equal,To prevent heavy,要用multimap
		//Manual changes to descending order
		multimap<int, string, greater<int>> intsort;
		for (const auto& e : mp)
		{
			//插入+排序
			intsort.insert(make_pair(e.second, e.first));
		}

		for (const auto& e : intsort)
		{
			cout << e.second << ":" << e.first << endl;
		}

	}
	return 0;
}

Analysis of how to realize the above：

To realize the dictionary order：

创建 map 对象 mp,单词作为 pair 类型的 key 值,次数作为 pair 类型的 value 值

输入一句话,while中用 getline 获取字符串,防止直接用 cin 遇到 ‘ ’ Stop getting directly

s 存放单个单词、slow Record each word starting subscript

for 循环下标遍历,Will change all capital letters is lower case

遇到 ' ' 或者 ‘ . ’ ,That must have in front of the word,This time you can to pick up the words：

The word is equal to the substring,我们用到 substr,num 为The word size,slowFor the word starting subscript

通过 i - slow,就可以算出The word size 

s 存储单词,用 s Insert the words to mp 中,并++,计数

最后要更新下一个单词的起始位置, slow = i + 1,Skip Spaces to the starting position of the next word

Implementation according to the number to the descending order of

这里用到 multimap ,multi Version allows keys redundant,次数作为 pair 类型的 key 值,单词作为 pair 类型的 value 值

将上述 pair Types of key/value pair is inserted into the multimap 的对象中,完成排序

注意：无论是map还是multimap,The default are compare key 值进行升序排列,Now in order to realize descending,Need to manually change the copy function

multimap<int, string, greater<int>> intsort;

 将 mp 对象的 first 和 second 交换位置,构建 intsort 对象的 pair

for (const auto& e : mp)
{
	//插入+排序
	intsort.insert(make_pair(e.second, e.first));
}

插入完成,Sorting is done,此时 intsort Object is stored in the output key/value pair is we need to：

for (const auto& e : intsort)
{
	cout << e.second << ":" << e.first << endl;
}

In accordance with the requirements for the output of the sample：Words in the front,The number in the,Output the entire content,这个题目就完成了.