Exercise · Operators and Expressions · lesson 8 of 8

Exercise: bit flags

A number flags stores a set of flags: flag number bit is on when bit number bit is 1. Write unsigned set_flag(unsigned flags, int bit) and unsigned clear_flag(unsigned flags, int bit): they return flags with that bit set to 1 or cleared to 0, and every other bit unchanged. The third function, bool has_flag(unsigned flags, int bit), returns true if that bit is 1.

set_flag(1u, 3) → 9u
clear_flag(9u, 0) → 8u
has_flag(2147483648u, 31) → true

Constraints: bit is from 0 to 31, and an unsigned takes 32 bits. Setting a bit that is already set, or clearing one that is already clear, returns flags unchanged.

flags.cpp — cpp

cpp · 12 lines

unsigned set_flag(unsigned flags, int bit) {
    return 0;
}

unsigned clear_flag(unsigned flags, int bit) {
    return 0;
}

bool has_flag(unsigned flags, int bit) {
    return false;
}

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