Question

我正在尝试实现二进制搜索来搜索char数组。执行时，程序重复说＆＃34;字母B在索引1＆＃34;尽管改变了输入，但永远不会改变。我不确定我哪里出错了。

#include <iostream>
#include <algorithm>
using namespace std;

bool binarySearch(char usedLetters[], int used, char letterToFind);

int main()
{
char a[] = {'A', 'B', 'C'};

int userValue;

cout << "Enter a letter: " << endl;
cin >> userValue;

int result = binarySearch(a, 8, userValue);

if(result == true)
{
    cout << "The letter " << a[result] << " was found at the"
            " element with index " << result << endl;
}
else
{
    cout << "The letter " << userValue << " was not found. " << endl;
}
}

bool binarySearch(char usedLetters[], int used, char letterToFind)
{
int first = 0;
int last = used - 1;
int mid;
int position = -1;
bool found = false;

while (!found && first <= last)
{
    mid = (first + last) / 2;
    if (usedLetters[mid] == letterToFind)
        {
            found = true;
            position = mid;
        }
    else if (usedLetters[mid] > letterToFind)
        last = mid - 1;
    else
        first = mid + 1;
}
return position;
}

Answer 1

您的二进制搜索返回bool，您返回的是找到该字母的位置，否则为-1。每次找到的位置与0不同时，您的函数将返回1（true），这就是为什么它始终输出它在索引1处找到B的原因。

只需更改二进制搜索即可返回int并将条件更改为：

if (result == -1)
    // Not found
else
    // Found

二进制搜索与字符数组

1 个答案: