[BOJ] 11049. 행렬 곱셈 순서

#include <iostream>
#include <vector>
#define MAXX 501
using namespace std;
 
typedef pair<int, int> pp;
typedef long long ll;
 
int dp[MAXX][MAXX];
 
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
 
    int n;
    cin >> n;
 
    vector<pp> matrix[MAXX];
    
    for (int i = 1; i <= n; i++) {
        int r, c;
        cin >> r >> c;
        matrix[i].push_back(pp(r, c));
    }
    
 
    for (int i = 1; i < n; i++) {
        dp[i][i+1] = matrix[i].front().first * matrix[i].front().second * matrix[i+1].front().second; 
    }
    //d[i][j] = i부터 j까지 곱했을 때 최소 연산 수 
    for (int len = 2; len <= n; len++) {
        for (int i = 1; i <= n-len; i++) {
            int j = i + len;
            for (int k = i; k < j; k++) {
                int tmp = dp[i][k]+dp[k+1][j]+ matrix[i].front().first * matrix[k].front().second * matrix[j].front().second;
                if (!dp[i][j] || tmp < dp[i][j]) dp[i][j] = tmp;
                
            }
        }
    }
    cout << dp[1][n] << '\n';
    return 0;
}