Fibonacci in C

fib.c

//O(n) in time, O(1) in space
int fib(int n) {
    int a, b, i, temp;
    a = 0;
    b = 1;
    for (i = 0; i < n; i++) {
        temp = a;
        a = a + b;
        b = temp;
    }
    return a;
}