Campus Bike II | BOTTOM UP DP

public int assignBikesMethod4(int[][] workers, int[][] bikes) {
    int dp[][] = new int[workers.length + 1][1 << bikes.length];
    for (int[] dpRow : dp) {
        Arrays.fill(dpRow, 20000);
    }
    int ans = MAX_VALUE;
    int n = workers.length;
    int m = bikes.length;
    dp[0][0] = 0;
    int combinations = 1 << m;
    for (int i = 1; i <= n; i++) {
        for (int mask = 1; mask < combinations; mask++) {
            for (int j = 0; j < m; j++) {
                if (checkSetBit(mask, j)) {
                    int prev = mask ^ (1 << j);
                    dp[i][mask] = min(dp[i - 1][prev] + manhattanDistance(workers[i - 1], bikes[j]), dp[i][mask]);
                    if (i == n) ans = Math.min(dp[i][mask], ans);
                }
            }
        }
    }
    return ans;
}