백준 - 1009번

#include <stdio.h>
#include <math.h>
 
int calc_number(int a, int b) {
    a %= 10;
    if (a == 0) return 10;
    else if (b == 1) return a;
    else if (a == 1 || a == 6 || a == 5) return a;
    else if (a == 4 || a == 9) {
        if ((b % 2) == 0) return ((a * a) % 10);
        else return a;
    }
    else {
        if ((b % 4) == 0) return (int)pow(a, 4) % 10;
        else return (int)pow(a, b % 4) % 10;
    }
}
 
int main() {
    int n, a, b;
    char result;
 
    scanf_s("%d", &n);
    for (int i = 0; i < n; i++) {
        scanf_s("%d %d", &a, &b);
        result = calc_number(a, b);
        printf("%d\n", result);
    }
    return 0;
}