Go: package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"strconv"
)

type Matrix struct {
	r int // num of row
	c int // num of column
}

type Range struct {
	start int // index, inclusive
	end   int // index, inclusive
}

func calcMultiplication(x, y Matrix) (Matrix, int) {
	if x.c != y.r {
		panic("cannnot calculate")
	}
	return Matrix{x.r, y.c}, x.r * y.c * x.c
}

func calcMinMatrixChainMultiplication(matrices []Matrix, r Range, memo map[Range]int) (Matrix, int) {
	if v, ok := memo[r]; ok {
		return Matrix{matrices[0].r, matrices[len(matrices)-1].c}, v
	}
	if len(matrices) == 0 {
		panic("must not be empty")
	} else if len(matrices) == 1 {
		return matrices[0], 0
	} else if len(matrices) == 2 {
		return calcMultiplication(matrices[0], matrices[1])
	}

	var minCount int = math.MaxInt32

	for i := 0; i < len(matrices)-1; i++ {
		formerMatrices := matrices[:i+1]
		latterMatrices := matrices[i+1:]
		matF, countF := calcMinMatrixChainMultiplication(formerMatrices, Range{0, i}, memo)
		matL, countL := calcMinMatrixChainMultiplication(latterMatrices, Range{i + 1, len(matrices) - 1}, memo)
		_, countFL := calcMultiplication(matF, matL)
		count := countF + countL + countFL
		if count < minCount {
			minCount = count
		}
	}
	return Matrix{matrices[0].r, matrices[len(matrices)-1].c}, minCount
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	n, _ := nextInt(sc)
	matrices := make([]Matrix, n)
	for i := 0; i < n; i++ {
		r, _ := nextInt(sc)
		c, _ := nextInt(sc)
		matrices[i] = Matrix{r, c}
	}
	memo := make(map[Range]int)
	_, resultCount := calcMinMatrixChainMultiplication(matrices, Range{0, len(matrices) - 1}, memo)
	fmt.Println(resultCount)
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

C++: #include <iostream>
#include <string>
#include <stack>
#include <queue>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <algorithm>

#include <cstdio>

using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep1(i, s, n) for (int i = (s); i <= (n); i++)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; i--)
#define rrep1(i, s, n) for (int i = (s); i >= (n); i--)
#define print_array(ary, size) cout << ary[0]; rep1(i, 1, size - 1) cout << ' ' << ary[i]; cout << endl;
typedef long long ll;
typedef unsigned long long ull;

int r[100];
int c[100];
int cost[100][100];

int getMulMin(int from, int to)
{
	int ret = 100000000;
	int cand;
	int div = to - from;

	if (cost[from][to] != -1) return cost[from][to];
	else if (div == 0) {
		cost[from][to] = 0;
		return 0;
	}

	rep(i, div) {
		cand = getMulMin(from, from + i) + getMulMin(from + i + 1, to) + r[from] * c[from + i] * c[to];
		ret = min(ret, cand);
	}

	cost[from][to] = ret;

	return ret;
}

int main()
{
	int n;
	int ans;

	rep(i, 100) {
		rep(j, 100) cost[i][j] = -1;
	}

	cin >> n;
	rep(i, n) cin >> r[i] >> c[i];

	ans = getMulMin(0, n - 1);
	cout << ans << endl;

	return 0;
}

C++: #include<string>
#include <utility>
#include <iostream>
 
#define MAX 100

#define INF 100000000

int left[MAX];
int right[MAX];

int DP[MAX][MAX];

int main(){
  int n;
  std::cin >> n;

  for(int i = 0; i < n; i++){
    std::cin >> left[i];
    std::cin >> right[i];
  }
  
  for(int i = 0; i < MAX; i++){
    for(int j = 0; j < MAX; j++){
      DP[i][j] = INF;
   }
  }

  for(int k = 0; k < n; k++){
    for(int l = 0; l + k < n; l++){
      int r = l + k;
      
      if(k == 0){
	DP[l][r] = 0;
      }else if(k == 1){
	DP[l][r] = left[l] * right[l] * right[r];
      }else{
	for(int t = l; t < r; t++){
	 
	  DP[l][r] = std::min(DP[l][r], DP[l][t] + DP[t + 1][r] + left[l] * right[t] * right[r]);
	}

	// printf("%d %d %d\n", l, r, DP[l][r]);
      }
    }
  }
  
  std::cout << DP[0][n-1] << std::endl;
}

C++: #include <bits/stdc++.h>

using namespace std;

using ll = long long;
using P = pair<ll, ll>;
using Graph = vector<vector<ll>>;
#define rep(i, n) for(ll i=0;i<(ll)(n);i++)
#define rep2(i, m, n) for(ll i=m;i<(ll)(n);i++)
#define rrep(i, n, m) for(ll i=n;i>=(ll)(m);i--)
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const int ddx[8] = {0, 1, 1, 1, 0, -1, -1, -1};
const int ddy[8] = {1, 1, 0, -1, -1, -1, 0, 1};
const ll MOD = 1000000007;
const ll INF = 1000000000000000000L;
#ifdef __DEBUG

/**
 * For DEBUG
 * https://github.com/ta7uw/cpp-pyprint
 */
#include "cpp-pyprint/pyprint.h"

#endif

ll N;
vector<P> A;
vector<vector<ll>> dp;

ll dfs(ll l, ll r) {
    if (dp[l][r] != INF) {
        return dp[l][r];
    }
    if (abs(l - r) == 1) {
        return dp[l][r] = 0;
    } else if (abs(l - r) == 2) {
        P f = A[l];
        P s = A[l + 1];
        return dp[l][r] = f.first * f.second * s.second;
    }

    ll res = INF;
    for (ll k = l + 1; k < r; k++) {
        res = min(res, dfs(l, k) + dfs(k, r) + A[l].first * A[r - 1].second * A[k - 1].second);
    }
    return dp[l][r] = res;
}

void solve() {
    cin >> N;
    A.resize(N);
    dp.resize(N + 1, vector<ll>(N + 1, INF));
    rep(i, N) cin >> A[i].first >> A[i].second;
    cout << dfs(0, N) << '\n';
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
    solve();
    return 0;
}

C++: //
//  main.cpp
//  ALDS1_10_B:MatrixChainMultiplication
//
//  Created by Kang on 2020/8/14.
//  Copyright © 2020 Kang. All rights reserved.
//

#include <cstdio>
using namespace std;

int main(int argc, const char * argv[]) {
    int n;
    int p[101];       // 矩阵维数
    int dp[101][101]; // 只用上三角
    
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        scanf("%d%d", &p[i], &p[i+1]);
    }
    // j-i = dif, dif = 0, 1, ..., n - 1
    for (int dif = 0; dif < n; dif++) {     // dif = j - i;
        for (int i = 1; i <= n-dif; i++) {  // i表示行数
            if(dif == 0) {dp[i][i] = 0;}
            else {
                int min = ~(1 << 31);
                int tmp;
                for (int k = i; k < i + dif; k++) {
                    tmp = dp[i][k] + dp[k + 1][i+dif] + p[i-1] * p[k] * p[i + dif];
                   /*printf("dp[%d][%d] + dp[%d][%d] + p[%d] * p[%d] * p[%d] = %d\n",
                          i, k, k+1, i+dif, i-1, k, i+dif, tmp);*/
                    if (tmp < min) min = tmp;
                }
                dp[i][i+dif] = min;
                
                // printf("dp[%d][%d] = %d\n",i, i+dif, min);
                // printf("--------------------\n");
            }
        }
    }
    printf("%d\n", dp[1][n]);
    
    return 0;
}

C++: #include<iostream>
#include<algorithm>
using namespace std;

static const int N = 100;

int main(){
  int n,p[N+1],m[N+1][N+1];
  cin >> n;
  for (int i=1;i<=n;i++){
    cin >> p[i-1] >> p[i];
  }

  for( int i=1;i<=n;i++)m[i][i]=0;
  for( int l=2;l<=n;l++){
    for( int i=1;i<=n-l+1;i++){
      int j=i+l-1;
      m[i][j]=(1<<21);
      for( int k=i;k<=j-1;k++){
        m[i][j]=min(m[i][j], m[i][k]+m[k+1][j]+p[i-1]*p[k]*p[j]);
        }
      }
    }

  cout << m[1][n] << endl;
  
  return 0;
}