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vector定义与初始化的巧妙用法
例子1:
代码中的8和3换成定义好的m和n变量,则无法通过编译。
代码:
#include <iostream>
#include <vector>
using namespace std;
int main() {
vector<int> mat[8](vector<int>(3));
for(int i = 0;i < 8;i++)
for(int j = 0;j < 3;j++)
mat[i][j] = i+j*3;
return 0;
}
结果:
(gdb) print mat
$1 = {std::vector of length 3, capacity 3 = {0, 3, 6}, std::vector of length 3, capacity 3 = {
1, 4, 7}, std::vector of length 3, capacity 3 = {2, 5, 8},
std::vector of length 3, capacity 3 = {3, 6, 9}, std::vector of length 3, capacity 3 = {4,
7, 10}, std::vector of length 3, capacity 3 = {5, 8, 11},
std::vector of length 3, capacity 3 = {6, 9, 12}, std::vector of length 3, capacity 3 = {7,
10, 13}}
例子2:
#include <iostream>
#include <vector>
using namespace std;
int main() {
int m = 3, n = 4;
vector<vector<int>> mat(m, vector<int>(n, 0));
for(int i = 0;i < m;i++)
for(int j = 0;j < n;j++)
mat[i][j] = i*2+j*3;
return 0;
}
运行结果:
(gdb) print mat
$1 = std::vector of length 3, capacity 3 = {std::vector of length 4, capacity 4 = {0, 3, 6,
9}, std::vector of length 4, capacity 4 = {2, 5, 8, 11},
std::vector of length 4, capacity 4 = {4, 7, 10, 13}}