Identifies the closest strength between 2 horses. Codingame puzzle at https://www.codingame.com/ide/puzzle/horse-racing-duals

codingame-horse-racing-duals.sh

read N
# An array of horses
declare -a horses
closest_strength=10000000
# Initialize last to -1 because it's an invalid value
last=-1
for (( i=0; i<N; i++ )); do
    read horse
    # We set the value as the key because it will be sorted automatically
    horses[$horse]=1
    #echo "Added horse ${horse}" >&2
done

# Show all keys of of the array (horses' strength) for debug
#echo "${!horses[@]}" >&2

# If the array length is < N then at least 2 horses have the same strength
if [[ "${#horses[@]}" -ne N ]] || [[ "${#horses[@]}" -eq 0 ]]; then
    closest_strength=0
else
    # For each key in array
    for i in ${!horses[@]}; do
        # If this is not the first loop (last not initialized with last value)
        if [ "$last" -ne -1 ]; then
            # Because the array is sorted, we know i>=last
            diff=$((i - last))
            #echo "diff:${diff}, last:${last}, i:${i} closest:$closest_strength" >&2
            if [ "$diff" -lt "$closest_strength" ]; then
                closest_strength=$diff
            fi;
        fi;
        last=$i
    done
fi;
echo "$closest_strength"