Go: // n×nの成長度表に現れる数字を重複を許してm-1個選んで掛け合わせる時の最大値を求める
// ->掛け算型のDP

package main

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

var scanner = bufio.NewScanner(os.Stdin)

func main() {
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		n, _ := strconv.Atoi(buf[0])
		m, _ := strconv.Atoi(buf[1])
		if n == 0 && m == 0 {
			break
		}
		growth_table := make([][]float64, n)
		for i := range growth_table {
			scanner.Scan()
			buf_ := strings.Split(scanner.Text(), " ")
			tmp := make([]float64, n)
			for j := range tmp {
				tmp[j], _ = strconv.ParseFloat(buf_[j], 64)
			}
			growth_table[i] = tmp
		}
		dp := make([][]float64, m)
		for i := range dp {
			dp[i] = make([]float64, n)
		}
		for i := range dp {
			dp[0][i] = 1
		}
		for k := 1; k < m; k++ {
			// k個使うとき...
			for i := 0; i < n; i++ {
				for j := 0; j < n; j++ {
					// 新たにgrowth_table[i][jを使うかどうか
					dp[k][j] = max(dp[k][j], dp[k-1][i]*growth_table[i][j])
					// check(dp)
				}
			}
		}
		ans := 0.0
		for i := 0; i < n; i++ {
			if dp[m-1][i] > ans {
				ans = dp[m-1][i]
			}
		}
		fmt.Printf("%.2f\n", ans)
	}
}

func max(a, b float64) float64 {
	if a < b {
		return b
	}
	return a
}

// func check(dp [][]float64) {
// 	log.Println()
// 	for i := range dp {
// 		log.Println(dp[i])
// 	}
// 	log.Println()
// }

C++: #include <iostream>
#include <stdio.h>
using namespace std;

int main() {
	int i,j,k,m,n;
	double a,d[100][100],an[100];
	while(cin >> n >> m) {
		if (n==0 && m==0) break;
		for (i=0;i<n;i++) { an[i]=1; for (j=0;j<n;j++) cin >> d[i][j];}
		for (k=0;k<m-1;k++) {
			for (i=0;i<n;i++) { a=0; 
			  for (j=0;j<n;j++) if (a<an[i]*d[j][i]) a=an[i]*d[j][i];
			   an[i]=a; 
		  }
	  }
	  for (i=0,a=0;i<n;i++) a= a < an[i] ? an[i] : a;
	  printf("%.2f\n",a);
  }  			  
  return 0;
}

C++: 
#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <cmath>
#include <utility>

#define ll (long long)
#define REP(i,n) for(int i = 0;i<(int)n;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--)


using namespace std;


int main(void){
    
    int drugnumber;
    int drugcounter;
    /* x????¨????,y?????´????????? */
    double drugeffect[120][120] = {0};
    int i,j,k,l;
    double max = 0;
    double answer[100] = {0};
    
    while(cin >> drugnumber >> drugcounter,drugnumber+drugnumber)
    {
        double combination[120][120] = {0};
        /*??£??\*/
        FOR(j, 1, drugnumber+1)
        FOR(i, 1, drugnumber+1)
        cin >> drugeffect[j][i];
        
        //cout << drugeffect[2][1];
        
        for(k = 1;k <= drugnumber; k++)
            combination[1][k] = 1.0;
        //cout << combination[1][2] << endl;
        
        /* j?????¬?????°,i????????°*/
        
        for(i = 1; i< drugcounter;i++)
            for(j = 1; j<= drugnumber;j++)
            {
                for(k = 1; k<=drugnumber;k++)
                {
                    if((combination[i][j] * drugeffect[j][k]) >= combination[i+1][k])
                        combination[i+1][k] = combination[i][j]*drugeffect[j][k];
                     //cout << combination[i+1][j] << " ";
                    /*
                     if((combination[j][i] * drugeffect[j][i]) >= combination[j][i])
                     combination[j][i+1] = combination[j][i] * drugeffect[j][i];
                     */
                }
            }
        
    
    for(i = 1 ; i<= drugnumber;i++)
        if(max <  combination[drugcounter][i])
            max = combination[drugcounter][i];
    
        answer[l] = max;
        max = 0;
        l++;
        
    }
    REP(i,l)
    printf("%.2f\n",answer[i]);
    return 0;
    
}

C++: #include<map>
#include<set>
#include<list>
#include<cmath>
#include<queue>
#include<stack>
#include<cstdio>
#include<string>
#include<vector>
#include<complex>
#include<cstdlib>
#include<cstring>
#include<numeric>
#include<sstream>
#include<iostream>
#include<algorithm>
#include<functional>

#define mp       make_pair
#define pb       push_back
#define all(x)   (x).begin(),(x).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,b,n) for(int i=b;i<n;i++)

using namespace std;

typedef    long long          ll;
typedef    unsigned long long ull;
typedef    vector<bool>       vb;
typedef    vector<int>        vi;
typedef    vector<vb>         vvb;
typedef    vector<vi>         vvi;
typedef    pair<int,int>      pii;

const int INF=1<<29;
const double EPS=1e-9;

const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};
int n,m;
const int MAX_N =120;
const int MAX_M =120;
double dp[MAX_N][MAX_M];//dp[i][j]:=直前にjを与え、i回目に肥料を与えたときの最大の成長
double memo[MAX_N][MAX_N];
int main(){
	while(1){
		cin>>n>>m;
		if(n==0&&m==0){
			break;
		}
		for(int i =0;i <MAX_N;i++){
			for(int j =0;j <MAX_N;j++){
				dp[i][j] =0;
				memo[i][j]=0;
			}
		}
		rep(i,n){
			rep(j,n){
				cin>>memo[i][j];
			}
		}
		bool flag =false;
		if(m==1){
			printf("%.2f\n",1.00);
			continue;
		}

		rep(i,n)dp[1][i] =1;

		double ans =0;
		for(int i =1;i <m;i++){
			for(int j =0;j <n;j++){//直後
				for(int k =0;k <n;k++){//直前
					dp[i+1][j] =max(dp[i+1][j],dp[i][k]*memo[j][k]);
					if(dp[i+1][j]>ans){
						ans =dp[i+1][j];
					}
				}
			}
		}
		ans +=0.005;
		ans =ans*100;
		ans =(int)ans;
		ans =(double)ans/100;
		printf("%.2f\n",m==1?1:ans);
	}
	return 0;
}

C++: # include <iostream>
# include <algorithm>
# include <iomanip>

# define MAX_N 100
# define MAX_M 100

int n, m;
double dp[MAX_N][MAX_M];

double board[MAX_M][MAX_M];

int main() {
	while (1) {
		std::cin >> n >> m;
		if (n == 0 && m == 0)
			break;
		for (int i = 0; i < n; ++i)
			for (int j = 0; j < m; ++j)
				dp[i][j] = 0;
		for (int i = 0; i < m; ++i) {
			for (int j = 0; j < m; ++j)
				std::cin >> board[i][j];
		}
		std::fill(dp[0], dp[0] + m, 1.0);
		for (int i = 1; i < n; ++i) {
			for (int j = 0; j < m; ++j) {
				for (int k = 0; k < m; ++k) {
					dp[i][j] = std::max(dp[i][j], dp[i - 1][k] * board[k][j]);
				}
			}
		}
		double res = 0;
		for (int i = 0; i < m; ++i)
			res = std::max(res, dp[n - 1][i]);
		std::cout << std::fixed << std::setprecision(2) << res << std::endl;
	}
	return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<cstdio>
#include<iomanip>

using namespace std;

int n, m;
double grow[100][100];
double dp[100][3];//

int main() {
	while (cin >> n >> m, n * m) {
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++) {
				cin >> grow[i][j];
			}
		}
		for (int i = 0; i < n; i++)dp[0][i] = 1;
		for (int i = 1; i < m; i++) {
			for (int j = 0; j < n; j++) {
				double M = 0;
				for (int k = 0; k < n; k++) {
					M = max(M, dp[i - 1][k] * grow[k][j]);
				}
				dp[i][j] = M;
			}
		}
		double ans = 0;
		for (int i = 0; i < n; i++) {
			ans = max(ans, dp[m - 1][i]);
		}
		int a = (ans + 0.005) * 100;
		ans = a;
		ans /= 100;
		cout << fixed << setprecision(2) << ans << endl;
		for (int i = 0; i < n; i++)for (int j = 0; j < n; j++)grow[i][j] = 0;
		for (int i = 0; i < m; i++)for (int j = 0; j < n; j++)dp[i][j] = 0;
	}
	return 0;
}

C++: #include <iostream>
#include <cmath>
#include <algorithm>

int n, m;
double grow[100][100];
double dp[110][110];

int main() {
    while(std::cin >> n >> m, n + m) {
    
    for(int i = 0; i < n; ++i) {
        for(int j = 0; j < n; ++j) {
            std::cin >> grow[i][j];
        }
    }

    for(int i = 0; i < n; ++i) {
        dp[0][i] = 1.;
    }
    for(int i = 1; i < n; ++i) {
        for(int j = 0; j < n; ++j) {
            dp[i][j] = 0.;
        }
    }

    for(int i = 1; i < m; ++i) {
        for(int j = 0; j < n; ++j) {
            for(int k = 0; k < n; ++k) {
                dp[i][j] = std::max(dp[i][j], dp[i - 1][k] * grow[k][j]);
            }
        }
    }

    printf("%.2f\n", ((int)(*std::max_element(dp[m - 1], dp[m - 1] + n) * 100 + 0.5)) / 100.);


    }
}