There are a row of n houses, each house can be painted with one of the k colors. The cost of painting each house with a certain color is different. You have to paint all the houses such that no two adjacent houses have the same color.
The cost of painting each house with a certain color is represented by a n x k cost matrix. For example, costs[0][0] is the cost of painting house 0 with color 0; costs[1][2] is the cost of painting house 1 with color 2, and so on... Find the minimum cost to paint all houses.
Note:
All costs are positive integers.
Example:
Input: [[1,5,3],[2,9,4]] Output: 5 Explanation: Paint house 0 into color 0, paint house 1 into color 2. Minimum cost: 1 + 4 = 5; Or paint house 0 into color 2, paint house 1 into color 0. Minimum cost: 3 + 2 = 5.
Follow up:
Could you solve it in O(nk) runtime?
struct Solution;
impl Solution {
fn min_cost_ii(costs: Vec<Vec<i32>>) -> i32 {
let n = costs.len();
if n == 0 {
return 0;
}
let m = costs[0].len();
let mut dp = vec![vec![0; m]; n];
for i in 0..m {
dp[0][i] = costs[0][i];
}
for i in 1..n {
for j in 0..m {
let mut min = std::i32::MAX;
for k in 0..m {
if k != j {
min = min.min(dp[i - 1][k]);
}
}
dp[i][j] = costs[i][j] + min;
}
}
dp[n - 1].iter().copied().min().unwrap()
}
}
#[test]
fn test() {
let costs = vec_vec_i32![[1, 5, 3], [2, 9, 4]];
let res = 5;
assert_eq!(Solution::min_cost_ii(costs), res);
}