为什么我必须初始化一个数组？

Question

So why do i have to do this "People[city][years] =1000 ;" thing?

int People[2059][100];
for (int city = 0; city < 2059; city++)
for (int years = 0; years < 100; years++)
People[city][years] = 1000;

Answer 1

You don't have to. But then the People array will contain indeterminate values, and reading them makes for a program with undefined behavior (I'm assuming that it's a variable with automatic storage duration). That's not an overly useful program.

If the array has static storage duration, then it will be zero-initialized. If you are okay with that, you don't have to loop over it and assign values immediately.

Answer 2

This line:

People[city][years] = 1000;

initializes the values in your 2D array to 1000 on the stack. If you don't initialize the numbers in your array, they can be anything.

Instead, you can initialize the numbers in People to 0 :

int People[2059][100] = {{0}}; /* or 1000, if you prefer that */

Using this instead saves you having to loop over the array and assign every value to 0 . If you decide to insert other numbers, then initializing the array won't be needed.