Paint House

You must paint n houses in a row, where the number of houses n is at least 1. The houses are indexed 0 to n-1.

You have three paint colors: red, green, and blue. The cost to paint house i a given color is provided in a 2D list costs, where:

• costs[i][0] is the cost of painting house i red
• costs[i][1] is the cost of painting house i green
• costs[i][2] is the cost of painting house i blue

No two neighboring houses may be painted the same color.

Write a function minCost(costs) that returns the smallest total cost to paint every house while obeying the adjacent-color restriction.

Example 1:

Input: costs = [[3, 5, 7]]

Output: 3

Explanation: There is one house. Painting it red costs 3, which is the cheapest option.

Example 2:

Input: costs = [[2, 4, 5], [3, 9, 1], [6, 8, 2]]

Output: 9

Explanation: An optimal assignment is:

• House 0 → red (cost 2)
• House 1 → blue (cost 1)
• House 2 → red (cost 6) Total cost = 9. The constraint on neighbors is satisfied since no two adjacent houses share a color.

Example 3:

Input: costs = [[10, 20, 30], [15, 15, 15], [5, 4, 3]]

Output: 28

Explanation: An optimal plan costs 28: house 0 → red (10), house 1 → green (15), house 2 → blue (3). No two consecutive houses share a color.

Constraints:

• n == costs.length
• 1 <= n <= 100
• costs[i].length == 3
• 0 <= costs[i][j] <= 1000