Branchless Grading

grade.c

#include <stdio.h>
#include <stdint.h>

int main()
{
    uint8_t buf[4] = {0};

    fgets(buf, sizeof(buf), stdin);

    int32_t i = (buf[2] << 8) | (buf[0]);

    int32_t g = (i - 0xA35) >> 31 & 0x33;
    g |= (~-g & (i - 0xA38)) >> 31 & buf[0];
    g |= ~-g >> 31 & 0x38;
    g = 0x79 - g;

    putchar(g);

    return 0;
}