Completed DP-2 exercises

[shreyargh]

No description provided.

[super30admin]

Strengths:

• The student has a good understanding of the problem and the intended approach (using DP with space optimization).
• The code is well-commented and follows good practices for readability.

Areas for Improvement:

• The logic for updating dp0, dp1, and dp2 is incorrect. The correct approach should start from the second last house (i=n-2) and move backwards, updating the costs based on the minimum of the other two colors for the next house.
• The iteration should start from i=n-2 (since the last house's costs are already initialized) and go down to i=0.
• The current implementation starts from i=1 and uses incorrect indices for accessing the costs array.

Suggested Correction:

class PaintHouse {
    public int minCost(int[][] costs) {
        if (costs == null || costs.length == 0) return 0;
        int n = costs.length;
        int dp0 = costs[n-1][0];
        int dp1 = costs[n-1][1];
        int dp2 = costs[n-1][2];

        for (int i = n-2; i >= 0; i--) {
            int temp0 = dp0;
            int temp1 = dp1;
            dp0 = costs[i][0] + Math.min(dp1, dp2);
            dp1 = costs[i][1] + Math.min(temp0, dp2);
            dp2 = costs[i][2] + Math.min(temp0, temp1);
        }

        return Math.min(dp0, Math.min(dp1, dp2));
    }
}