Why do array element values not change?

int a[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

for (int i = 0; i <= 9; i++) {
    int tmp = a[i];
    a[i] = a[9 - i];
    a[9 - i] = tmp;
}

for (int i = 0; i <= 9; i++) {
    printf("%d", a[i]);
}

The result of it is: 1234567890,
but why not 10987654321
since it switch values in the first for loop,
but why can not change it when the next for loop runs

I have tried to move "int tmp" outside of the loop, but of no use at all.

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