Go: package main

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

// Define disjoint-set forests

type vertexNo int

type vertex struct {
	number vertexNo
	rank int
	parent *vertex
}

func makeSet(number vertexNo) vertex {
	return vertex {
		number: number,
		rank: 0,
		parent: nil,
	}
}

func union(x, y *vertex) *vertex {
	return link(findSet(x), findSet(y))
}

func link(x, y *vertex) *vertex {
	if x.rank > y.rank {
		y.parent = x
		return x
	} else {
		x.parent = y
		if x.rank == y.rank {
			y.rank += 1
		}
		return y
	}
}

func findSet(v *vertex) *vertex {
	if v.parent == nil {
		return v
	}
	v.parent = findSet(v.parent)
	return v.parent
}

// Function to calculate minimum spanning tree

type matrix [][]int

type edge struct {
	one vertexNo
	two vertexNo
	weight int
}

const(
	MAX_VERTICES = 100
)

func newEdgesFromMatrix(matrix matrix) []edge {
	edges := make([]edge, 0, MAX_VERTICES * MAX_VERTICES)

	for i := 0; i < len(matrix); i++ {
		row := matrix[i]
		for j := i; j < len(row); j++ {
			if row[j] >= 0 {
				edge := edge{one: vertexNo(i+1), two: vertexNo(j+1), weight: row[j]}
				edges = append(edges, edge)
			}
		}
	}

	return edges
}

func solve(matrix matrix) int {
	nVertices := len(matrix)

	// initialize vertices
	vertices := make([]vertex, nVertices)
	for i := 0; i < nVertices; i++ {
		vertices[i] = makeSet(vertexNo(i+1))
	}

	// prepare edges sorted in the ascending order of weight
	edges := newEdgesFromMatrix(matrix)
	sort.Slice(edges, func(i, j int) bool {
		return edges[i].weight < edges[j].weight
	})

	unionCount := 0
	weightSum := 0
	for unionCount < nVertices-1 {
		for i := 0; i < len(edges); i++ {
			edge := edges[i]
			v1 := &vertices[edge.one-1]
			v2 := &vertices[edge.two-1]
			rep1 := findSet(v1)
			rep2 := findSet(v2)
			if rep1.number == rep2.number {
				continue
			}
			union(rep1, rep2)
			edges = append(edges[0:i], edges[i+1:]...)
			weightSum += edge.weight
			unionCount++
			break
		}
	}

	return weightSum
}

// main

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}

	matrix := parseMatrix(n, sc)

	edges := newEdgesFromMatrix(matrix)
	sort.Slice(edges, func(i, j int) bool {
		return edges[i].weight < edges[j].weight
	})

	fmt.Println(solve(matrix))
}

func parseMatrix(n int, sc *bufio.Scanner) [][]int {
	matrix := make([][]int, n)
	for i := 0; i < n; i++ {
		matrix[i] = make([]int, n)
		for j := 0; j < n; j++ {
			x, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			matrix[i][j] = x
		}
	}
	return matrix
}

func nextText(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

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

C++: /**
 * @copyright (c) 2020 Daisuke Hashimoto
 */

#include <algorithm>
#include <cstdint>
#include <functional>
#include <iostream>
#include <queue>
#include <string>
#include <utility>
#include <vector>

constexpr int32_t kMaxNumberOfVertices = 100;
constexpr int32_t kInvalidIndex = -1;

void CallPrimAlgorithm(std::istream &input_stream);

struct Edge {
  int32_t to{kInvalidIndex};
  int32_t weight{INT32_MAX};
};

struct Vertex {
  bool assigned_to_tree{false};
  std::vector<Edge> neighbours;
};

class PrimAlgorithm {
 public:
  PrimAlgorithm() noexcept;
  ~PrimAlgorithm() noexcept;
  void SetNumberOfVertices(const int32_t number_of_vertices) noexcept;
  void AddVertex(const int32_t from, const int32_t to, const int32_t weight) noexcept;
  void BuildMinimumSpanningTree(const int32_t start_vertex_index) noexcept;
  int32_t GetSumOfWeightsOfMst() const noexcept;

 private:
  void AddToTree(const int32_t child, const int32_t weight) noexcept;

 private:
  int32_t number_of_vertices_;
  int32_t sum_of_weights_;
  Vertex vertices_[kMaxNumberOfVertices];
  using Pair = std::pair<int32_t, int32_t>;
  std::priority_queue<Pair, std::vector<Pair>, std::greater<Pair>> priority_queue_;
};

void CallPrimAlgorithm(std::istream &input_stream) {
  input_stream.tie(0);
  std::ios::sync_with_stdio(false);
  PrimAlgorithm *minimum_spanning_tree = new PrimAlgorithm();
  try {
    int32_t number_of_vertices;
    input_stream >> number_of_vertices;
    minimum_spanning_tree->SetNumberOfVertices(number_of_vertices);
    for (int32_t from = 0; from < number_of_vertices; ++from) {
      for (int32_t to = 0; to < number_of_vertices; ++to) {
        int32_t weight;
        input_stream >> weight;
        if (weight >= 0) {
          minimum_spanning_tree->AddVertex(from, to, weight);
        }
      }
    }
    constexpr int32_t kStartVertex = 0;
    minimum_spanning_tree->BuildMinimumSpanningTree(kStartVertex);
    const int32_t sum_of_weights = minimum_spanning_tree->GetSumOfWeightsOfMst();
    std::cout << sum_of_weights << std::endl;
  } catch (...) {
    std::cerr << "ERROR: CallPrimAlgorithm()" << std::endl;
    throw;
  }
  delete minimum_spanning_tree;
}

// ****************************************************
PrimAlgorithm::PrimAlgorithm() noexcept : number_of_vertices_(0), sum_of_weights_(0) {}

PrimAlgorithm::~PrimAlgorithm() noexcept {}

void PrimAlgorithm::SetNumberOfVertices(const int32_t number_of_vertices) noexcept {
  number_of_vertices_ = number_of_vertices;
}

void PrimAlgorithm::AddVertex(const int32_t from, const int32_t to, const int32_t weight) noexcept {
  Edge edge1;
  edge1.to = to;
  edge1.weight = weight;
  vertices_[from].neighbours.push_back(edge1);
}

void PrimAlgorithm::BuildMinimumSpanningTree(const int32_t start_vertex_index) noexcept {
  constexpr int32_t kZeroDistance = 0;
  priority_queue_.push(Pair(kZeroDistance, start_vertex_index));
  while (priority_queue_.size() > 0) {
    const int32_t c_distance = priority_queue_.top().first;
    const int32_t c_vertex_index = priority_queue_.top().second;
    priority_queue_.pop();
    if (!vertices_[c_vertex_index].assigned_to_tree) {
      AddToTree(c_vertex_index, c_distance);
      for (const Edge &c_edge : vertices_[c_vertex_index].neighbours) {
        const int32_t neighbour_index = c_edge.to;
        if (!vertices_[neighbour_index].assigned_to_tree) {
          priority_queue_.push(Pair(c_edge.weight, neighbour_index));
        }
      }
    }
  }
}

int32_t PrimAlgorithm::GetSumOfWeightsOfMst() const noexcept {
  return sum_of_weights_;
}

void PrimAlgorithm::AddToTree(const int32_t child, const int32_t weight) noexcept {
  vertices_[child].assigned_to_tree = true;
  sum_of_weights_ += weight;
}

// **********************************************************************

int main() {
  try {
    CallPrimAlgorithm(std::cin);
  } catch (...) {
    std::cerr << "ERROR: main()" << std::endl;
  }
  return 0;
}

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

int n;
int a[101];

void print() {
    cout << a[0];
    for (int i = 1; i < n; i++) {
        cout << " " << a[i];
    }
    cout << endl;
}

int main() {
    while (cin >> n) {
        for (int i = 0; i < n; i++) {
            cin >> a[i];
        }
        print();
        for (int j = 1; j < n; j++) {
            int key = a[j];
            int i = j - 1;
            while (0 <= i && key < a[i]) {
                a[i + 1] = a[i];
                i--;
            }
            a[i + 1] = key;
            print();
        }
    }
}