c++学习笔记(5)

二维数组：
数组声明：  int matrix[2][2] = {{1,2}, {3,4}}

数组索引： 嵌套循环：

二维数组初始化+随机洗牌（reshuflle）

code:

#include <iostream>
#include <cmath>
#include <iomanip>
#include <cstdlib>
#include <time.h>

using namespace std;

const int ROW_SIZE = 10;
const int COL_SIZE = 10;

void printMatrix(int matrix[][COL_SIZE], int row, int col); 
void reshuffleMatrix(int matrix[][COL_SIZE], int, int);
int matrixSum(int matrix[][COL_SIZE], int, int);

int main(int argc, char *argv[])
{
	//srand(time(0));
	int matrix[ROW_SIZE][COL_SIZE];
	for(int row=0; row<ROW_SIZE; row++)
	{
		for(int col=0; col<COL_SIZE; col++)
		{
			matrix[row][col] = row + col;
		}
	}
	cout << "The matrix before reshuffle: " << endl;
	printMatrix(matrix, ROW_SIZE, COL_SIZE);
	reshuffleMatrix(matrix, ROW_SIZE, COL_SIZE);
	cout << "The matrix after reshuffle: " << endl;
	printMatrix(matrix, ROW_SIZE, COL_SIZE);
	int mat_sum = matrixSum(matrix, ROW_SIZE, COL_SIZE);
	cout << "The sum of the matrix is " << mat_sum << endl;
	 
	return 0;
}

void printMatrix(int matrix[][COL_SIZE], int row, int col)
{
	for(int i=0; i<row; i++)
	{
		for(int j=0; j<col; j++)
		{
			cout << setw(4) << matrix[i][j] << "  ";
		}
		cout << endl;
	}
}

void reshuffleMatrix(int matrix[][COL_SIZE], int row, int col)
{
	srand(time(0));
	for(int i=0; i<ROW_SIZE; i++)
	{
		for(int j=0; j<COL_SIZE; j++)
		{
			int rand_i = rand() % ROW_SIZE;  // 
			int rand_j = rand() % COL_SIZE;
			
			// swap the matrix
			int tmp = matrix[i][j];
			matrix[i][j] = matrix[rand_i][rand_j];
			matrix[rand_i][rand_j] = tmp;
		}
	}
}

int matrixSum(int matrix[][COL_SIZE], int row, int col)
{
	int sum = 0;
	for(int i=0; i<ROW_SIZE; i++)
	{
		for(int j=0; j<COL_SIZE; j++)
		{
			sum += matrix[i][j];
		}
	}
	return sum;
}

二维数组做为函数参数：
C++规定，二维数组作为函数参数，必须声明二维数组的列的大小。

问题：找最近邻点对。

#include <iostream>
#include <cmath> 

using namespace std;

double getDistance(double, double, double, double);

int main(int argc, char *argv[])
{
        const int NUMBER_OF_POINT = 8;
        double point[NUMBER_OF_POINT][2];
        // 输入点的数据
        cout << "Enter " << NUMBER_OF_POINT << " Points." << endl;
	for(int i=0; i<NUMBER_OF_POINT; i++)
	{
		cin >> point[i][0] >> point[i][1];
	} 
	int p1 = 0;
	int p2 = 1;
	double shortest_distance = getDistance(point[p1][0], point[p1][1], point[p2][0], point[p2][1]);
	// 计算点之间的距离 
        for(int i=0; i<NUMBER_OF_POINT-1; i++)
	{
		for(int j=i+1; j<NUMBER_OF_POINT; j++)
		{
			double tmp_distance = getDistance(point[i][0], point[i][1], point[j][0], point[j][1]);
			cout << "Distance is " << tmp_distance << endl;
			if(tmp_distance < shortest_distance)
			{
				shortest_distance = tmp_distance;
				p1 = i;    // 记录下坐标 
				p2 = j;
			}
		}
	} 
	cout << "The shotrst distance is " << shortest_distance << endl;
	cout << "The point is " << "(" << point[p1][0] << "," << point[p1][1] << ")" << " and " << "(" << point[p2][0] << "," << point[p2][1] << ")" << endl;
	return 0;
}

double getDistance(double x1, double y1, double x2, double y2)
{
	return sqrt(pow(x1-x2, 2) + pow(y1-y2, 2));
}

结果：

改进： 如果有多个最小点怎么找到

数度游戏

给定一个数独问题的解，验证其是否正确

即需要验证：

（1）每一行的姐是否满足条件

（2）每一列的解是否满足条件

（3）每一个3X3的网格内是否满足条件

#include <iostream>
#include <cmath> 

using namespace std;

bool isValid(int, int, int grid[][9]);
bool isValid(int grid[][9]);

int main(int argc, char *argv[])
{
    int solution[9][9] = {
    	                  {5,3,4,6,7,8,9,1,2},
    	                  {6,7,2,1,9,5,3,4,8},
						  {1,9,8,3,4,2,5,6,7},
						  {8,5,9,7,6,1,4,2,3},
						  {4,2,6,8,5,3,7,9,1},
						  {7,1,3,9,2,4,8,5,6},
						  {9,6,1,5,3,7,2,8,4},
						  {2,8,7,4,1,9,6,3,5},
	                      {3,4,5,2,8,6,1,7,9}
                         };
	 
	if(isValid(solution))
	{
		cout << "The Sudoku solution is legal " << endl;
	}
	else
	{
	    cout << "The Sudoku solution is illegal" << endl;	
	}
	return 0;
}

bool isValid(int i, int j, int grid[][9])
{
   // 判断数独的解是否合法
   for(int col=0; col<9; col++)   // 判断第i行 
   {
   	  if(col!=j && grid[i][j]==grid[i][col])
   	      return false;
   }
   
   for(int row=0; row<9; row++)   // 判断第j列 
   {
   	  if(row!=i && grid[row][j]==grid[i][j])
		 return false; 
   }	
   
   for(int row=(i/3)*3; row<(i/3)*3+3; row++)    // 注意这里的处理方法，很重要 
   {
   	 for(int col=(j/3)*3; col<(j/3)*3+3; col++)
     {
 	    if(row!=i && col!=j && grid[row][col]==grid[i][j])
		   return false;  	
     }
   }
   return true;
}

bool isValid(int grid[][9])
{
	for(int i=0; i<9; i++)
	{
	   for(int j=0; j<9; j++)
	   {
   	      if(grid[i][j]<1 || grid[i][j] >9 || !isValid(i, j, grid))
			 return false;	
   	   }	
	}
	return true;
}

多维数组作为参数：

猜生日：多维数组解决

#include <iostream>
#include <cmath> 
#include <iomanip>

using namespace std;


int main(int argc, char *argv[])
{
    int day = 0;
    char answer;
    int dates[5][4][4] = {
	                         {
	    	                  {1,3,5,7},
	    	                  {9,11,13,15},
							  {17,19,21,23},
							  {25,27,29,31}, 
		                     },
		                     {
		                     	{2,3,6,7},
		                     	{10,11,14,15},
			                    {18,19,22,23},
								{26,27,30,31} 
      			             },
      			             {
             			      	{4,5,6,7},
								{12,13,14,15},
								{20,21,22,23},
								{28,29,30,31} 
             			      },
             			      {
      			             	{8,9,10,11},
								{12,13,14,15},
								{24,25,26,27},
								{28,29,30,31} 
      			             },
      			             {
             			      	{16,17,18,19},
								{20,21,22,23},
								{24,25,26,27},
								{28,29,30,31} 
             			      }
                         };
	for(int i=0; i<5; i++)
	{
		cout << "Is your birthday in set ?" << endl;
		for(int j=0; j<4; j++)
		{
			for(int k=0; k<4; k++)
			{
				cout << setw(3) << dates[i][j][k];
			}
			cout << endl;
		}
		cout << endl << "Enter yes or no(y/n)" << endl;
		cin >> answer;
		if(answer=='y' || answer=='Y')
		    day += dates[i][0][0];
	}
	cout << "Your birthday is " << day << endl;
	return 0;
}