掏宝笔试编程题

题目的大概意思是，编程输出dev[1-4,a][b,c]的展开形式，如下：

dev1b

dev1c

dev2b

dev2c

dev3b

dev3c

dev4b

dev4c

devab

devac

 

 

解：回溯法，主要是展开[]字符有些麻烦

 

#include <iostream> #include <stack> #include <vector> #include <iomanip> #include <cstring> #include <cassert> using namespace std; #define DEBUG static void do_extend(const char *t, vector< vector<char> > &array) { vector<char> str; char tmp; assert('[' == *t); while (']' != *t){ t++; /*skip [*/ str.push_back(*t); /*'a-' or 'a,' or 'a'*/ t++; if (',' == *t){ t++; str.push_back(*t); t++; }else if ('-' == *t){ tmp = *(t - 1); /*start*/ t++; /*end*/ tmp++; /*skip start*/ while (*t != tmp){ str.push_back(tmp); tmp++; } str.push_back(tmp); t++; } } array.push_back(str); } static void extend_element(vector<const char *> &s, vector< vector<char> > &array) { for (vector<const char *>::iterator it = s.begin(); it != s.end(); it++){ do_extend(*it, array); } } static void print_name(vector<char> &prefix, vector<char> &suffix, vector< vector<char> > &array, vector< vector<char> >::iterator it) { if (array.end() == it){ for (vector<char>::iterator it1 = prefix.begin(); it1 != prefix.end(); it1++){ cout << *it1; } for (vector<char>::iterator it1 = suffix.begin(); it1 != suffix.end(); it1++){ cout << *it1; } cout << endl; }else{ /*line it*/ for (vector<char>::iterator it1 = (*it).begin(); it1 != (*it).end(); it1++){ suffix.push_back(*it1); /*in*/ print_name(prefix, suffix, array, it + 1); suffix.pop_back(); /*out*/ } } } int main() { const char *str = "dev[1-4,7][a-z,3-9]"; vector< vector<char> > array; vector<const char *> s; vector<char> prefix, suffix; const char *t, *t1; t = strchr(str, '['); for (t1 = str; t1 != t; t1++){ prefix.push_back(*t1); } t = str; while ((t = strchr(t, '['))){ s.push_back(t); #ifdef DEBUG cout << *t << endl; #endif t++; } #ifdef DEBUG cout << s.size() << endl; #endif extend_element(s, array); #ifdef DEBUG for (vector< vector<char> >::iterator it1 = array.begin(); it1 != array.end(); it1++){ for (vector<char>::iterator it2 = (*it1).begin(); it2 != (*it1).end(); it2++){ cout << *it2 << " "; } cout << endl; } #endif print_name(prefix, suffix, array, array.begin()); return 0; }