Find paths to consume all tickets

FindPath.ts

const data: Record<string, Set<string>> = {
    MUM: new Set(['CHEN']),
    BLR: new Set(['JAI']),
    DEL: new Set(['BLR', 'AGRA']),
    JAI: new Set(['MUM']),
    AGRA: new Set(['DEL'])
};

function findStart(data: Record<string, Set<string>>) {
    const source: Record<string, number> = {};
    const dest: Record<string, number> = {};
    const startingPoints: string[] = [];
    for (let [key, value] of Object.entries(data)) {
        source[key] = value.size;
    }

    for (let destinations of Object.values(data)) {
        for (let destination of destinations) {
            if (!dest[destination]) {
                dest[destination] = 1;
            } else {
                dest[destination]++;
            }
        }
    }

    for (let destination of Object.keys(dest)) {
        dest[destination] -= source[destination] || 0;
        if (dest[destination] === -1) {
            startingPoints.push(destination);
        }
    }

    if (startingPoints.length === 1) {
        return startingPoints[0];
    } else if (startingPoints.length > 1) {
        return '';
    }

}

function findPath(data: Record<string, Set<string>>, start: string) {
    const path = [];
    let currentSource = start;

    
    while (currentSource && data[currentSource]) {

        if (!data[currentSource]) {
            return path;
        }

        if (data[currentSource].size === 0) {
            return path;
        }

        if (data[currentSource].size === 1) {
            let currentDestination = data[currentSource].values().next().value;
            path.push([currentSource, currentDestination]);
            currentSource = currentDestination;
        }

        if (data[currentSource] && data[currentSource].size > 1) {
            for (let destination of data[currentSource].values()) {
                if (data[destination] && data[destination].has(currentSource)) {
                    data[currentSource].delete(destination);
                    path.push([currentSource, destination]);
                    currentSource = destination;
                }
            }
        }


    }

    return path;
}

const startingPoint = findStart(data);
console.log(`Starting point: `, startingPoint);

const paths = findPath(data, startingPoint);

let result = '';
result += `${paths[0][0]} --> `;

for (let path of paths) {
    result += `${path[1]} --> `;
}

console.log(result.slice(0, -5));