题解 | #[NOIP2010]数字统计#

#include <stdio.h>
int checkTwo(int l, int r) {
    int tmp = 0, cnt = 0;
    for (int i = l; i <= r; i++) {
        tmp = i;
        while (tmp) {
            // Check LSB(Least Significant Bit)
            if (tmp % 10 == 2) {
                cnt++;
            }
            // Check the next digit of tmp
            tmp /= 10;
        }
    }
    return cnt;
}

int main() {
    int l, r;
    while (scanf("%d %d", &l, &r) != EOF) {
        printf("%d\n", checkTwo(l, r));
    }
    return 0;
}