题目:在一个二维数组中,每一行都按照从左到右递增的顺序排序,每一列都按照从上到下递增的顺序排序。请完成一个函数,输入这样的一个二维数组和一个整数,判断数组中是否含有该整数。
思路:这题和堆排序有类似,查找过程中从右上方的数字开始,如果该数字比查找的数字小,那么该数字所在行可以删除,不用继续考虑;如果该数字比查找的数字大,那么该数字所在列可以删除。这样,每次执行,都会删除一行或者一列,极端情况下,执行2n次。
1 #include "stdafx.h" 2 #include<stdio.h> 3 4 bool Find(int* matrix, int rows, int columns, int number) 5 { 6 bool found = false; 7 8 if(matrix != NULL && rows > 0 && columns > 0) 9 { 10 int row = 0; 11 int column = columns - 1; 12 while(row < rows && column >= 0) 13 { 14 if(matrix[row*columns + column] == number) 15 { 16 found = true; 17 printf("the number %d is in row: %d and column: %d ", number, row+1, column +1); 18 break; 19 } 20 else if(matrix[row*columns + column] > number) 21 -- column; 22 else 23 ++ row; 24 } 25 } 26 27 return found; 28 } 29 30 void Test(char* testName, int* matrix, int rows, int columns, int number, bool expected) 31 { 32 if(testName != NULL) 33 printf("%s begins. ", testName); 34 35 bool result = Find(matrix, rows, columns, number); 36 if(result == expected) 37 printf("Passed. "); 38 else 39 printf("Failed. "); 40 } 41 42 void Test1() 43 { 44 int matrix[][4] = {{1,2,8,9}, {2,4,9,12},{4,7,10,13},{6,8,11,15}}; 45 Test("Test1", (int*)matrix, 4,4,7,true); 46 } 47 48 // 1 2 8 9 49 // 2 4 9 12 50 // 4 7 10 13 51 // 6 8 11 15 52 int main() 53 { 54 int rows = 4; 55 int columns = 4; 56 int number = 7; 57 int matrix[][4] = {{1,2,8,9}, {2,4,9,12},{4,7,10,13},{6,8,11,15}}; 58 59 for(int i = 0 ; i < rows; i++) 60 { 61 for(int j = 0 ;j < columns; j++) 62 printf("%d ", matrix[i][j]); 63 64 printf(" "); 65 } 66 printf(" "); 67 bool result = Find((int*)matrix, rows, columns, number); 68 if(result) 69 printf("found. "); 70 else 71 printf("not found. "); 72 73 return 0; 74 }