POJ 2418 Hardwood Species （map）
阿新 • • 發佈：2020-08-08
題目通道：POJ 2418
第一次用map，中間費了點周折，string類的輸入輸出一直存在問題，string類不能scanf直接輸入，要提前預訂大小，string a; a.resize(100); scanf("%s",&a[0]); 如果多個字串輸入，用getline(cin, s)即可，空格也能讀入
| Describe: |
| Hardwoods are the botanical group of trees that have broad leaves, produce a fruit or nut, and generally go dormant in the winter. 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：
給一堆樹的名字，問每種樹的個數佔比多少，按字典序輸出，保留四位小數。
題目思路：
思路是沒難度，用map做就是記錄每個樹個數，最後算一下就行，主要是map的一些操作熟練一下，printf不能直接輸出string類，得用string.c_str()函式程式設計字元陣列再輸出。
AC程式碼：
1 #include <iostream> 2 #include <cstdio> 3 #include <map> 4 #include <string> 5 using namespace std; 6 int main() 7 { 8 map<string, double> m; // 建立map 9 map<string, double>::iterator iter; // 建立迭代器型別 10 string s; 11 int n = 0; // 計數器 12 while(getline(cin,s)) // 可以讀入空格，學到了 13 { 14 m[s]++; 15 n++; 16 } 17 for(iter=m.begin(); iter!=m.end(); iter++) // 遍歷map，輸出 18 { 19 printf("%s %.4f\n",(iter->first).c_str(),(iter->second)*100.0/n); 20 } 21 return 0; 22 }