How to use the Resize function in C + +

Resize (), set the size (size);
Reserve (), set the capacity (capacity);
Size () is the amount of memory allocated to the container, and capacity () simply sets the container capacity, but does not actually allocate memory.
For example: A bus being built, the car can be set up 40 seats (Reserve (40), this is its capacity, but not that it has 40 seats, can only show that the car interior space can be placed under 40 seats. With 40 seats in the car (resize);), this time the car actually has 40 seats, these seats can be used

How to use the Resize function in C + +