算法百题006：单词逆序输出（Word Reversal）

声明：转载或引用代码请注明 http://blog.csdn.net/fduan/archive/2011/05/11/6411199.aspx

 

For each list of words, output a line with each word reversed without changing the order of the words.

This problem contains multiple test cases!

The first line of a multiple input is an integer N, then a blank line followed by N input blocks. Each input block is in the format indicated in the problem description. There is a blank line between input blocks.

The output format consists of N output blocks. There is a blank line between output blocks.

Input

You will be given a number of test cases. The first line contains a positive integer indicating the number of cases to follow. Each case is given on a line containing a list of words separated by one space, and each word contains only uppercase and lowercase letters.

Output

For each test case, print the output on one line.

Sample Input

1

3
I am happy today
To be or not to be
I want to win the practice contest

Sample Output

I ma yppah yadot
oT eb ro ton ot eb
I tnaw ot niw eht ecitcarp tsetnoc

 

 

 

分析：此题有三个关键点，一是文件的I/O，二是字符串切割，三是单词的逆序。

 

下面给出各关键点的实现。

 

关键一：字符串切割

void split_string( const string & str, std::vector<string> & words ) { words.clear(); typedef string::size_type string_size; string_size i = 0; while( i != str.size() ) { while( i != str.size() && isspace( str[i] ) ) ++i; string_size j = i; while( j != str.size() && !isspace(str[j])) ++j; if( i != j ) { words.push_back( str.substr( i, j - i ) ); i = j; } } }

 

关键二：单词逆序，借助标准库中的vector和reverse实现。

void reverse_words( const vector<string> & words ) { string word; for( int k = 0; k < words.size() - 1; ++k ) { word = words[k]; reverse( word.begin(), word.end() ); cout << word << " "; } word = words[ words.size() - 1]; if( word.size() > 1 ) reverse( word.begin(), word.end() ); cout << word << endl; }

 

关键三：文件读取

int main() { ifstream cin("data.txt"); int n; cin >> n; for( int i = 0; i < n; ++i ) { string line; // skip space line getline( cin, line ); int num_lines; cin >> num_lines; for( int j = 0; j < num_lines; ++j ) { vector<string> words; // skip '/n' char c; if( j == 0) c = cin.get(); getline( cin, line ); split_string( line, words ); reverse_words( words ); } if( i < n - 1) cout << endl; } return 0; }