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.
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
題目大意：給你一些字符串，讓你統計每個字符串出現的概率。
解題思路：此題我是用Trie樹來寫的，用map可能會TLE。輸出字符串的時候要求按字典序，於是我就用了dfs。
Ps：這道題在POJ上是單組數據，但在ZOJ上是多組數據，請大家注意！另外，此題中的字符串中可能會包含除字母外的其他字符，大家小心！
請看代碼：
#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#define mem(a , b) memset(a , b , sizeof(a) )
using namespace std ;
const int MAXN = 3e5 + 5 ;
char A[50] ;
int vis[MAXN] ; // 建立標記數組，用於最後輸出字符串
int cnt ; // 給Trie樹中每個結點設定編號
int sum ; // 統計字符串的個數
struct Tnode
{
int count ; // 統計該結點出現的單詞個數
char f ; // 記錄Trie樹中結點所存的字符
int xu ; // 記錄Trie樹中結點的序號
Tnode * next[256] ; // 數組開大一些，因為可能會包含除字母外的其他字符。
Tnode()
{
count = 0 ;
f = 0 ;
xu = 0 ;
mem(next , 0) ;
}
} ;
char s[50] ;
void inse(char * str , Tnode * root)
{
Tnode * p = root ;
int id ;
while (*str)
{
id = *str - '\0' ;
if(p -> next[id] == 0)
{
p -> next[id] = new Tnode ;
p -> next[id] -> xu = ++ cnt ;
p -> next[id] -> f = *str ;
}
p = p -> next[id] ;
++ str ;
}
p -> count ++ ;
}
double ans ;
void print(int deep , Tnode * p) // dfs 按字典序輸出字符串 ， deep為遞歸的深度
{
int i ;
for(i = 0 ; i < 256; i ++ )
{
if(p -> next[i] != NULL)
{
int tmp = p -> next[i] -> xu ;
A[deep] = p -> next[i] -> f ;
if(p -> next[i] -> count > 0 && !vis[tmp])
{
vis[tmp] = 1 ;
ans = p -> next[i] -> count * 100.0 / sum * 1,0;
int j ;
for(j = 0 ; j <= deep ; j ++)
{
printf("%c" , A[j]) ;
}
printf(" %.4f\n" ,ans) ;
}
print(deep + 1 , p -> next[i]) ;
}
}
}
int main()
{
bool flag = false ;
while (gets(s))
{
if(flag) // 相鄰兩組數據間輸出一個空行
printf("\n") ;
else
flag = true ;
cnt = 0 ;
sum = 0 ;
Tnode * root = new Tnode ;
memset(vis , 0 , sizeof(vis)) ;
inse(s , root) ;
sum ++ ;
while (gets(s) && strlen(s))
{
inse(s , root) ;
sum ++ ;
}
print(0 , root) ;
}
return 0 ;
}
