我在C ++中运行二进制搜索算法,但它给了我虚假的结果。例如,搜索值21会给我一个
“找到价值”
消息,但我的数组只包含0到20之间的数字。
非常感谢任何帮助。
#include <iostream>
#include <iomanip>
using namespace std;
int binarySearch(const int [], int, int, int, int ); // function prototype
int main()
{
const int arraySize = 10;
int arr[ arraySize ];
int key;
for( int i = 0; i <= arraySize; i++) // generate data for array
arr[i] = 2*i;
cout << "The array being searched is: " << endl;
for (int j = 0; j<=arraySize; j++) // print subscript index of the array
{
cout << setw(5) << j << " ";
}
cout << endl;
for (int z = 0; z<=arraySize; z++) // print elements of the array below index
{
cout << setw(5) << arr[z] << " ";
}
cout << "\n" <<"Enter value you want to search in array " << endl;
cin >> key;
int result = binarySearch(arr, key, 0, arraySize, arraySize); // function call
if (result == 1) // print result of search
cout << "Key is found " << endl;
else
cout << "Key not found " << endl;
return 0;
} // end main function
int binarySearch(const int a[], int searchKey, int low, int high, int length)
{
int middle;
while (low <= high){
middle = (low + high) / 2;
if (searchKey == a[middle]) // search value found in the array, we have a match
{
return 1;
break;
}
else
{
if( searchKey < a[middle] ) // if search value less than middle element
high = middle - 1; // set a new high element
else
low = middle + 1; // otherwise search high end of the array
}
}
return -1;
}
答案 0 :(得分:4)
您正在调用undefined behavior,因为您的for
循环条件为<=arraySize
。将其更改为<arraySize
。在进行此更改时,代码可以完美地用于样本输入。
通过编写int arr[ arraySize ];
,您正在创建一个包含10个元素的数组(即,从0
到9
),而在for循环中,您从0
开始移至10
。
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