c++中vector和数组的互相转换

分类：C++, Others 阅读 (16,127) Add comments

5月 052016

转载请注明原文地址：http://bcoder.com/others/convert-between-vector-and-array-in-cplusplus

1. vector转数组: 使用memcpy将vector中的数据拷贝到数组中

注意: memcpy的第三个参数，拷贝长度必须乘以sizeof(vec[0])

#include <vector>
#include <iostream>

using std::vector;

int main(void){
	//初始化为10个c字符
	vector<unsigned char> vec(10, 'c');
	unsigned char charary[vec.size()];

	//vector全部转到数组
	memcpy(charary, &vec[0], vec.size() * sizeof(vec[0]));

	for(int i = 0; i != sizeof(charary); ++i){
		std::cout << charary[i] ;
	}
	std::cout << std::endl;



	//转部分vector数据到数组，最后4个
	unsigned char ary1[4];
	memcpy(ary1, &vec[6], 4);

	for(int i = 0; i != sizeof(ary1); ++i){
		std::cout << ary1[i] ;
	}
	std::cout << std::endl;

	return 0;
}

#include <vector>

#include <iostream>

using std::vector;

int main(void){

//初始化为10个c字符

vector<unsigned char> vec(10, 'c');

unsigned char charary[vec.size()];

//vector全部转到数组

memcpy(charary, &vec[0], vec.size() * sizeof(vec[0]));

for(int i = 0; i != sizeof(charary); ++i){

std::cout << charary[i] ;

}

std::cout << std::endl;

//转部分vector数据到数组，最后4个

unsigned char ary1[4];

memcpy(ary1, &vec[6], 4);

for(int i = 0; i != sizeof(ary1); ++i){

std::cout << ary1[i] ;

}

std::cout << std::endl;

return 0;

}

2. 数组转vector：使用vector的初始化构造函数

注意：这个版本的vector的构造函数，第一个参数为源数据的指针起始地址，第二个参数为要拷贝的个数（~~不是内存字节长度~~），所以要除以一个sizeof(int)

#include <vector>
#include <iostream>

using std::vector;

int main(void){
	int ary[] = {10, 18, 9, 1, 66, 0, 102, 32, 99, 70};
	vector<int> vec(ary, ary + sizeof(ary) / sizeof(int));
	for(int i = 0; i != vec.size(); ++i){
		std::cout << vec[i] << ", ";
	}
	std::cout << std::endl;

	return 0;
}

#include <vector>

#include <iostream>

using std::vector;

int main(void){

int ary[] = {10, 18, 9, 1, 66, 0, 102, 32, 99, 70};

vector<int> vec(ary, ary + sizeof(ary) / sizeof(int));

for(int i = 0; i != vec.size(); ++i){

std::cout << vec[i] << ", ";

}

std::cout << std::endl;

return 0;

}

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