0743-network-delay-time.java

// Bellman Ford ALgorithm
// Time Complexty (n * t) | Space Complexity O(n) where t is the length of times
class Solution {

    public int networkDelayTime(int[][] times, int n, int k) {
        // initialize an array with max value of size n
        int[] paths = new int[n];
        Arrays.fill(paths, Integer.MAX_VALUE);

        paths[k - 1] = 0;

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

            // loop through times
            for (int j = 0; j < times.length; j++) {
                int src = times[j][0]; // source
                int tgt = times[j][1]; // target
                int time = times[j][2]; // time

                if (
                    temp[src - 1] != Integer.MAX_VALUE &&
                    temp[src - 1] + time < temp[tgt - 1]
                ) {
                    temp[tgt - 1] = temp[src - 1] + time;
                }
            }

            // set paths to temp
            paths = temp;
        }

        int result = Integer.MIN_VALUE;

        // calculate max value
        for (int i = 0; i < n; i++) {
            if (paths[i] == Integer.MAX_VALUE) {
                return -1;
            }
            result = Math.max(result, paths[i]);
        }

        // return result
        return result;
    }
}