In C ++, the STL container type is used as a function and does not use references, which leads to a decrease in program efficiency. stl containers

In C ++, the STL container type is used as a function and does not use references, which leads to a decrease in program efficiency. stl containers

I recently found a problem with algorithm questions:

I implement an algorithm recursively, but in the TreeNode * createTree Function(Vector <int> & num, Int left, int right)

TreeNode * createTree (Vector <int> num, Int left, int right), The result always times out,

I found some algorithms written by others on the Internet and found that they are all implemented in that way. Finally, I found that the parameter types of functions are different,

When someone else uses the vector type as a parameter, the reference is passed, and I directly use the form parameter of the function, resulting in every function recursion, all the values of the num array must be copied, which greatly affects the program efficiency.

Finally, I changed it to use reference, which greatly improved the efficiency of the result program!

Summary:

When parameters such as vector, queue, and stack are involved in c ++,Be sure to use & as parametersOtherwiseData Copying, Resulting in a much lower efficiency of the entire program!