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 (r Range) length() int {
	return r.end - r.start + 1
}

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[r.start].r, matrices[r.end].c}, v
	}
	if r.length() == 0 {
		panic("must not be empty")
	} else if r.length() == 1 {
		return matrices[r.start], 0
	}

	var minCount int = math.MaxInt32

	for i := 0; i < r.length()-1; i++ {
		formerRange := Range{r.start, r.start + i}
		latterRange := Range{r.start + i + 1, r.end}
		matF, countF := calcMinMatrixChainMultiplication(matrices, formerRange, memo)
		matL, countL := calcMinMatrixChainMultiplication(matrices, latterRange, memo)
		_, countFL := calcMultiplication(matF, matL)
		count := countF + countL + countFL
		if count < minCount {
			minCount = count
		}
	}
	memo[r] = minCount
	return Matrix{matrices[r.start].r, matrices[r.end].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++: //
//  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;
}

C++: #include <iostream>
#include <iomanip>
#include <utility>
#include <cmath>
#include <random>
#include <vector>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <algorithm>
using namespace std;

#define rep(i,n) for(int i = 0; i<n; ++i)
#define REP(i,n) for(int i = 1; i<=n; ++i)
#define all(x) begin(x),end(x)
#define show(obj) {for(auto x:obj)cout<<x<<' ';cout<<endl;}
typedef long long ll;
typedef pair<int,int> ip;
typedef pair<ll,ll> lp;
const int inf = 1001001000;
const ll INF = 1LL<<60;
const int MOD = (int)1e9 + 7;

template<class T> inline bool chmin(T& a, T b) {if (a > b) { a = b; return true; } return false;}

int main(){
	int N; cin>>N;
	vector<ip> M(N);
	rep(i,N)cin>>M[i].first>>M[i].second;
	vector<vector<int>> dp(N,vector<int>(N,inf));
	rep(i,N)dp[i][i] = 0;
	for(int i = 1; i<N; ++i){
		int l = 0, r = i;
		for(int j = 0; j<N-i; ++j){
			for(int k = l; k<r; ++k){
				chmin(dp[l][r], dp[l][k] + dp[k+1][r] + M[l].first * M[k].second * M[r].second);
				// chmin(dp[l][r], dp[l][r-1] + M[l].first * M[r].first * M[r].second);
			}
			// printf("[l,r] => [%d,%d]\n",l,r);
			++l; ++r;
		}
	}
	cout<<dp[0][N-1]<<endl;
	return 0;
}

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

int nlist[110];
int dp[110][110];

int main(){
  int n;
  cin>>n;
  for(int i=0;i<n;i++){
    cin>>nlist[i]>>nlist[i+1];
  }
  for(int i=1;i<n;i++){
    for(int j=0;j<n-i;j++){
      dp[j][j+i]=1<<30;
      for(int k=0;k<i;k++){
	dp[j][j+i]=min(dp[j][j+i],dp[j][j+k]+dp[j+k+1][j+i]+nlist[j]*nlist[j+k+1]*nlist[j+i+1]);
      }
    }
  }
  cout<<dp[0][n-1]<<endl;
  return 0;
}

C++: #include "bits/stdc++.h"
using namespace std;
typedef long long ll;
// #define int long long

template <class T>
bool INRANGE(T x, T a, T b) { return a <= x && x <= b; }

#define REP(i, n) for (int i = 0; i < (n); ++i)
#define RREP(i, n) for (int i = (n); i >= 0; --i)
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define RFOR(i, a, b) for (int i = (a); i >= (b); --i)
#define ALL(v) (v).begin(), (v).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" \
                      << " " << __FILE__ << endl;
#define DUMP(list) cout << "{ "; for(auto nth : list){ cout << nth << " "; } cout << "}" << endl;
typedef vector<int> vi;
typedef vector<string> vs;
typedef vector<vi> vvi;
typedef pair<int, int> pii;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n;
    cin >> n;

    vi p(102);
    REP(i, n) cin >> p[i] >> p[i+1];
    vvi dp(102, vi(102, 0));

    FOR(l, 2, n+1){           // 対象とする行列の数
        FOR(i, 1, n-l+2){     
            int j = i + l - 1;   
            dp[i][j] = (1 << 20); // dp[i][j] := [Mi, Mj]の最小回数
            FOR(k, i, j){
	            dp[i][j] = min(dp[i][j], dp[i][k] + dp[k+1][j] + p[i-1] * p[k] * p[j]);
            }
        }
    }

  cout << dp[1][n] << endl;

    
}

C++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e18;
const int inf = 1e9;
double pi = 3.14159265359;
#define rep(i, a, b) for (int i = a; i < b; i++)
#define per(i, b, a) for (int i = a - 1; i >= b; i--)
using Graph = vector<vector<int>>;
using pint = pair<int, int>;
int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
int dxx[8] = {1, 1, 1, 0, 0, -1, -1, -1}, dyy[8] = {-1, 0, 1, -1, 1, -1, 0, 1};

int main() {
    int n;
    cin >> n;
    int p[n + 1];
    rep (i, 1, n + 1) cin >> p[i - 1] >> p[i];
    int dp[n + 1][n + 1]; // i->jまでの計算をする時の最小回数
    rep (i, 0, n + 1) dp[i][i] = 0;
    rep (i, 2, n + 1) {
        rep (j, 1, n - i + 2) {
            int k = i + j - 1;
            dp[j][k] = inf;
            rep (l, j, k) {
                dp[j][k] = min (dp[j][k], dp[j][l] + dp[l + 1][k] +
                                              p[j - 1] * p[l] * p[k]);
            }
        }
    }
    cout << dp[1][n] << "\n";
}