550f22f4d758534c1100025a

solution.ts

export type tDirection = 'NORTH' | 'SOUTH' | 'EAST' | 'WEST';
export const opposites = {
    EAST: 'WEST',
    NORTH: 'SOUTH',
    SOUTH: 'NORTH',
    WEST: 'EAST',
};

export function dirReduc(arr: string[]): tDirection[] {
    const output = [...arr] as tDirection[];

    const iterate = (): boolean => {
        let changed = false;
        let index = 0;

        while (index < output.length - 1) {
            const current = output[index];
            const next = output[index + 1];

            if (opposites[current] !== next) {
                index++;
                continue;
            }

            output.splice(index + 1, 1);
            output.splice(index, 1);
            changed = true;
        }

        return changed;
    };

    let changing = true;
    while (changing) {
        changing = iterate();
    }

    return output;
}