LeetCode-Search a 2D Matrix

Search a 2D Matrix

 Total Accepted: 35062 Total Submissions: 111591

Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:

• Integers in each row are sorted from left to right.
• The first integer of each row is greater than the last integer of the previous row.

For example,

Consider the following matrix:

[
  [1,   3,  5,  7],
  [10, 11, 16, 20],
  [23, 30, 34, 50]
]

Given target = 3, return true

MySolution :

bool
searchMatrix(int **matrix, int m, int n, int target)
{
    int i;
    int j;
    int InHalf = 0;
    if( m <=0 || n <= 0 )
        return false;
    if( m <= 1 && n <= 1 )
    {
        return matrix[m-1][n-1] == target;
    }
    
    InHalf = (int)(n/2)-1;
    
    if( n <= 1 )
    {
        InHalf = 0;
    }
    
    if( target < matrix[0][0] || target > matrix[m-1][n-1] )
        return false;
    for( i = 0; i < m; i++ )
    {
        if( target >= matrix[i][0] && target <= matrix[i][n-1] )
        {
            if( target <= matrix[i][InHalf] )/* n/2 */
            {
                for( j = 0; j <=InHalf; j++ )
                {
                    if( target == matrix[i][j] )
                        return true;
                }
            }
            else/* target >= matrix[i][InHalf] */
            {
                for( j = InHalf+1; j <= n-1; j++ )
                {
                    if( target == matrix[i][j] )
                        return true;
                }
            }
        }
    }
    return false;
}

Submission Result: Accepted

地址：Search a 2D Matrix

RunTime:

在做这个题目的时候遇到了一个初始化问题。代码例如以下：

#include <stdio.h>
#include <stdlib.h>

#define bool    int
#define false   0
#define true    1



bool searchMatrix(int **matrix, int m, int n, int target);


bool
searchMatrix(int **matrix, int m, int n, int target)
{
    int i;
    int j;
    int InHalf = 0;

    InHalf = (int)(n/2)-1;
    for( i = 0; i < 3; i++ )
        for( j = 0; j < 4; j++)
            printf("%d\n",matrix[i][j]);
    if( target < matrix[0][0] || target > matrix[m-1][n-1] )
        return false;
    for( i = 0; i < m; i++ )
    {
        if( target >= matrix[i][0] && target <= matrix[i][n-1] )
        {
            if( target <= matrix[i][InHalf] )/* n/2 */
            {
                for( j = 0; j <=InHalf; j++ )
                {
                    if( target == matrix[i][j] )
                        return true;
                }
            }
            else/* target >= matrix[i][InHalf] */
            {
                for( j = InHalf+1; j <= n-1; j++ )
                {
                    if( target == matrix[i][j] )
                        return true;
                }
            }
        }
    }
    return false;
}

int main(void)
{
    int i;
    int m=3,n=4;
    int iReturn = false;
    int** pMatrix2D = malloc( sizeof( int* )*m );
    pMatrix2D[0] = malloc( sizeof( int )*m*n );
    for( i = 1; i < 3; i++)
    {
        pMatrix2D[i] = pMatrix2D[i-1] + 4;
    }
    pMatrix2D[0][0] = 1;
    pMatrix2D[0][1] = 3;
    pMatrix2D[0][2] = 5;
    pMatrix2D[0][3] = 7;

    pMatrix2D[1][0] = 10;
    pMatrix2D[1][1] = 11;
    pMatrix2D[1][2] = 16;
    pMatrix2D[1][3] = 20;

    pMatrix2D[2][0] = 23;
    pMatrix2D[2][1] = 30;
    pMatrix2D[2][2] = 34;
    pMatrix2D[2][3] = 50;

    iReturn = searchMatrix( pMatrix2D, m, n, 3 );
    printf( "%d ",iReturn );
    return 0;
}

问题參考