若要將vector中反過來列印,該怎麼做呢?STL提供了reverse_iterator。
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/*
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(C) OOMusou 2006 http://oomusou.cnblogs.com
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Filename : ReverseIterator.cpp
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Compiler : Visual C++ 8.0 / ISO C++
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Description : Demo how to use reverse_iterator
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Release : 12/17/2006 1.0
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*/
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#include <iostream>
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#include <vector>
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#include <algorithm>
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using namespace std;
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int main() {
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int ia[] = {1, 2, 3};
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vector<int> ivec(ia, ia + sizeof(ia) / sizeof(int));
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// use reverse_iterator by for loop
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for(vector<int>::reverse_iterator r_iter = ivec.rbegin(); r_iter != ivec.rend(); ++r_iter)
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cout << *r_iter << " ";
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cout << endl;
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// use ordinary iterator to print reversely
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for(vector<int>::const_iterator iter = (--ivec.end()); iter >= ivec.begin();iter--) {
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cout << *iter << " ";
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if (iter == ivec.begin())
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break;
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}
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cout << endl;
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// use reverse_iterator with copy() algorithm
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copy(ivec.rbegin(), ivec.rend(), ostream_iterator<int>(cout, " "));
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cout << endl;
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}
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執行結果
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19行的for loop,使用了reverse_iterator,讓我們很簡單的如操作一般的iterator般去處理reverse_iterator。
25行到29行,使用了一般的iterator去處理,程式有點詭異,主要是讓我們看出,若沒有reverse_iterator,程式有多難寫。
copy() algorithm也可搭配reverse_iterator,只需一行就可以了。