(经典map)A - Hardwood Species（7.1.1）（利用STL中自带的排序功能编程的实验范例）
Description
Hardwoods are the botanical group of trees that have broad leaves, produce a fruit or nut, and generally go dormant in the winter.
America's temperate climates produce forests with hundreds of hardwood species -- trees that share certain biological characteristics. Although oak, maple and cherry all are types of hardwood trees, for example, they are different species. Together, all the hardwood species represent 40 percent of the trees in the United States.
On the other hand, softwoods, or conifers, from the Latin word meaning "cone-bearing," have needles. Widely available US softwoods include cedar, fir, hemlock, pine, redwood, spruce and cypress. In a home, the softwoods are used primarily as structural lumber such as 2x4s and 2x6s, with some limited decorative applications.
Using satellite imaging technology, the Department of Natural Resources has compiled an inventory of every tree standing on a particular day. You are to compute the total fraction of the tree population represented by each species.
America's temperate climates produce forests with hundreds of hardwood species -- trees that share certain biological characteristics. Although oak, maple and cherry all are types of hardwood trees, for example, they are different species. Together, all the hardwood species represent 40 percent of the trees in the United States.
On the other hand, softwoods, or conifers, from the Latin word meaning "cone-bearing," have needles. Widely available US softwoods include cedar, fir, hemlock, pine, redwood, spruce and cypress. In a home, the softwoods are used primarily as structural lumber such as 2x4s and 2x6s, with some limited decorative applications.
Using satellite imaging technology, the Department of Natural Resources has compiled an inventory of every tree standing on a particular day. You are to compute the total fraction of the tree population represented by each species.
Input
Input to your program consists of a list of the species of every tree observed by the satellite; one tree per line. No species name exceeds 30 characters. There are no more than 10,000 species and no more than 1,000,000 trees.
Output
Print the name of each species represented in the population, in alphabetical order, followed by the percentage of the population it represents, to 4 decimal places.
Sample Input
Red Alder Ash Aspen Basswood Ash Beech Yellow Birch Ash Cherry Cottonwood Ash Cypress Red Elm Gum Hackberry White Oak Hickory Pecan Hard Maple White Oak Soft Maple Red Oak Red Oak White Oak Poplan Sassafras Sycamore Black Walnut Willow
Sample Output
Ash 13.7931 Aspen 3.4483 Basswood 3.4483 Beech 3.4483 Black Walnut 3.4483 Cherry 3.4483 Cottonwood 3.4483 Cypress 3.4483 Gum 3.4483 Hackberry 3.4483 Hard Maple 3.4483 Hickory 3.4483 Pecan 3.4483 Poplan 3.4483 Red Alder 3.4483 Red Elm 3.4483 Red Oak 6.8966 Sassafras 3.4483 Soft Maple 3.4483 Sycamore 3.4483 White Oak 10.3448 Willow 3.4483 Yellow Birch 3.4483
其实在map中，map<int,string> personnel;中的int是一个索引项，就是相当于数组中的下标，用来作为查找的标记
在输入新的字符串时，如果是已经存在的字符串则不再开辟新的空间，就会使用原来的空间，但是没有的话就会在开辟一个索引项为当前输入字符串的空间
可以通过map中的size函数来验证（参考网址 ）
其他map函数（网址 http://blog.csdn.net/u014665013/article/details/38141315）
另外在定义时是否可以通过字符数组来索引还有待验证！！！
#include<iostream>
#include <cstdio>
#include <string>
#include <cstring>
#include <map>
#include <vector>
using namespace std;
typedef map<string ,int >record;
record h;
string s;
int n;
int main()
{
n=0;
while(getline(cin,s)) /////默认为文件结束才输出结果
{
n++;
h[s]++;//对当前的int数据加1
}
record::iterator it ;//定义map（容器）指针
for(it=h.begin();it!=h.end();it++)//从开始到结束对所有数值进行输出注意 h.begin（）是第一个，但h.end()不是最后一个，而是在里面已经没有值了
{
string name=it->first;//对该变量的第一个即为字符串
int k=it->second;//输出对应的数据
printf("%s %.4lf\n",name.c_str(),double(k)*100/double(n)); //这里name.c_str()是一个转换函数，
//因为printf不能输出字符串（string）必须将其转换为char组类型的有待验证
}
return 0;
}