0787-cheapest-flights-within-k-stops.java

// Time Complexity O(k * n) | Space Complexity O(n)
class Solution {

    public int findCheapestPrice(
        int n,
        int[][] flights,
        int src,
        int dst,
        int k
    ) {
        // initialize an array with max value of size n
        int[] prices = new int[n];
        Arrays.fill(prices, Integer.MAX_VALUE);

        // price from source to source is always 0
        prices[src] = 0;

        for (int i = 0; i <= k; i++) {
            // make a copy of prices
            int[] temp = new int[n];
            temp = Arrays.copyOf(prices, prices.length);

            // loop through flights
            for (int j = 0; j < flights.length; j++) {
                int s = flights[j][0]; // from
                int d = flights[j][1]; // to
                int p = flights[j][2]; // price

                if (prices[s] == Integer.MAX_VALUE) {
                    continue;
                }

                if (prices[s] + p < temp[d]) {
                    temp[d] = prices[s] + p;
                }
            }

            // set prices to temp
            prices = temp;
        }

        if (prices[dst] != Integer.MAX_VALUE) {
            return prices[dst];
        }

        return -1;
    }
}