resize()與reserve()都是vector容器中的方法：

resize():改變了capacity()和size()

reserve():增加了vector的capacity()，但是它的size()沒有改變

#include <iostream>
#include <stdio.h>
#include <vector>
#include<functional>
using namespace std;

int main(int argc, char* argv[])
{
? ? vector<int> v;
? ? vector<int>::iterator it;
? ? vector<int> v2;

? ? v.push_back(1);
? ? v.push_back(2);
? ? v.push_back(3);
? ? v.push_back(4);
? ? v.push_back(11);
? ? v.push_back(12);
? ? v.push_back(13);
? ? v.push_back(14);

? ? v2.push_back(21);
? ? v2.push_back(22);
? ? v2.push_back(23);
? ? v2.push_back(24);
? ? v2.push_back(25);
? ? v2.push_back(26);
? ? v2.push_back(27);
? ? v2.push_back(28);

? ? cout << "original data v:" << "===========start============" << "\n";
? ? for (it = v.begin(); it != v.end(); ++it) {
? ? ? ? cout << *it << endl;
? ? }
? ? cout << "original data v:" << "============end===========" << "\n";

? ? cout << "original data v:" << ": capacity()=" << v.capacity() << ", size()=" << v.size() << "\n";

? ? v.resize(10); //改變capacity()和size()

? ? cout << "after resize data" << ": capacity()=" << v.capacity() << ", size()=" << v.size() << "\n";
? ? for (it = v.begin(); it != v.end(); ++it) {
? ? ? ? cout << *it << endl;
? ? }

? ? cout << "original data v2:" << "===========start============" << "\n";
? ? for (it = v2.begin(); it != v2.end(); ++it) {
? ? ? ? cout << *it << endl;
? ? }
? ? cout << "original data v2:" << "============end===========" << "\n";

? ? cout << "original data v2:" << ": capacity()=" << v2.capacity() << ", size()=" << v2.size() << "\n";

? ? v2.reserve(10); ?//只增加了capacity()
? ? cout << "after reserve data" << ": capacity()=" << v2.capacity() << ", size()=" << v2.size() << "\n";

? ? return 0;
}

根據上面的打印可以看出：

vector.resize():改變了capacity()和size()

vector.reserve():增加了vector的capacity()，但是它的size()沒有改變

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