Unix ls, UVa 400

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题目

The computer company you work for is introducing a brand new computer line and is developing a new Unix-like operating system to be introduced along with the new computer. Your assignment is to write the formatter for the ls function.
Your program will eventually read input from a pipe (although for now your program will read from the input file). Input to your program will consist of a list of (F) filenames that you will sort (ascending based on the ASCII character values) and format into (C) columns based on the length (L) of the longest filename. Filenames will be between 1 and 60 (inclusive) characters in length and will be formatted into left-justified columns. The rightmost column will be the width of the longest filename and all other columns will be the width of the longest filename plus 2. There will be as many columns as will fit in 60 characters. Your program should use as few rows (R) as possible with rows being filled to capacity from left to right.

Input

The input file will contain an indefinite number of lists of filenames. Each list will begin with a line containing a single integer (1<=N<=100). There will then be N lines each containing one left-justified filename and the entire line’s contents (between 1 and 60 characters) are considered to be part of the filename. Allowable characters are alphanumeric (a to z,A to Z, and 0 to 9) and from the following set{._-} (not including the curly braces). There will be no illegal characters in any of the filenames and no line will be completely empty.Immediately following the last filename will be the N for the next set or the end of file. You should read and format all sets in the input file.

Output

For each set of filenames you should print a line of exactly 60 dashes (-) followed by the formatted columns of filenames. The sorted filenames 1 to R will be listed down column 1; filenames R+1 to 2R listed down column 2;etc.

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题意

输入正整数n以及n个文件名，排序后用尽可能少的行左对齐输出。

分析

关键在于每行最多60个字符，以此条件和最长文件名的length，求出最多能有多少列，然后按列输出即可。

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代码实现

#include<iostream>#include<string>#include<algorithm>using namespace std;const int maxcol = 60;const int maxn = 100 + 5;string filenames[maxn];// 输出字符串s，长度不足len时补字符extravoid print(const string& s, int len, char extra) {  cout << s;  for(int i = 0; i < len-s.length(); i++)    cout << extra;}int main() {  int n;  while(cin >> n) {    int M = 0;    for(int i = 0; i < n; i++) {      cin >> filenames[i];      M = max(M, (int)filenames[i].length());    }    // 计算列数cols和行数rows    int cols = (maxcol - M) / (M + 2) + 1, rows = (n - 1) / cols + 1;    print("", 60, '-');    cout << "\n";    sort(filenames, filenames+n);    for(int r = 0; r < rows; r++) {      for(int c = 0; c < cols; c++) {        int idx = c * rows + r;        if(idx < n) print(filenames[idx], c == cols-1 ? M : M+2, ' ');      }      cout << "\n";    }  }  return 0;}

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