C++动态规划解决矩阵连乘问题

小咪咪 2022-08-13 21:00 186阅读 0赞

#include<iostream>
    #include<iomanip>
    using namespace std;
    
    fun(int l,int n,int m[]) {
    	int i,j,k,r;
    	int **a = new int*[n];
    	for(i=0;i<n;i++) {
    		a[i] = new int[n];
    	}
    	for(i=0;i<n;i++) {
    		for(j=0;j<n;j++) {
    			a[i][j] = 0;
    		}
    	}
    	for(i=0;i<n;i++) {
    		for(j=0,k=i;k!=n;j++,k++) {
    			if(j==k) a[j][k] = 0;
    			else {
    				int min = 1000000;
    				for(r=j;r<k;r++) {
    					int temp = a[j][r] + a[r+1][k] + m[j] * m[r+1] * m[k+1];
    					cout<<m[j] * m[r+1] * m[k]<<endl;
    					if(temp < min) min = temp;
    				}
    				a[j][k] = min;
    				cout<<j<<":"<<k<<endl;
    			}
    		}
    	}
    	return a[0][n-1];
    }
    
    int main() {
    	int n[] = {50,10,40,30,5};
    	cout<<fun(0,4,n)<<endl;
    	return 0;
    }

<------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------>

#include<iostream>
    using namespace std;
    
    //运用动态规划的思想解决矩阵连乘问题
    int matrixMul(int i, int j, int p[]) {
        int **array;//array[i][j]
        array = new int*[j + 1];
        for (int k1 = 0; k1 < j + 1; k1++) {
            array[k1] = new int[j + 1];
    
            for (int k2 = 0; k2 < j + 1; k2++)
                array[k1][k2] = 0;
        }
    
        for (int f = 1; f < j + 1; f++) {
            for (int k1 = i, k2 = f; k1 < j + 1 && k2 < j + 1; k1++, k2++) {
                int min = 100000000;
                if (k1 == k2)
                    break;
                for (int k = k1; k < k2; k++) {
                    int temp = array[k1][k] + array[k + 1][k2] + p[k1 - 1] * p[k] * p[k2];
                    if (temp < min)
                        min = temp;
                }
    
                array[k1][k2] = min;
            }
        }
        
        return array[i][j];
    }
    
    int main() {
        int p[] = { 50, 10, 40, 30, 5 };
        int result = matrixMul(1, 4, p);
        cout << result << endl;
    
        return 0;
    }