关于二分查找调换了判断条件却得到不同结果

Question

打开第一个条件语句能够正确输出"target(-11) has been found, 关闭它之后再打开第二个条件语句却输出"no targer", 两个条件语句只是调换了判断条件, 为什么结果会不一样呢

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

class Solution {
public:
    static int search(vector<int>& arr, int target) {
            if (target<arr[0] || target>*(arr.end() - 1)) //如果目标在超出容器范围就不必寻找
                return -1;

        int left = 0; //头指针
        int right = arr.size(); //尾指针

        while (left < right) {
            int middle = (left + right) >> 1; //中间值
#if 1 //第一个条件语句能够正确输出结果
            if (arr[middle] < target)
                left = middle + 1;
            else
                right = middle;
#endif
#if 0 //第二个条件语句不能输出正确结果
            if (target < arr[middle])
                right = middle;
            else
                left = middle + 1;
#endif 
        }
        return (arr[left] == target ? left : -1);
    }
};

int main() {
    vector<int> arr = {-11,-1,2,4,5,7,9,11,34,55,67 };
    int index = Solution::search(arr, -11);
    if (index != -1)
        cout << "target(" << arr[index] << ") has been found" << endl;
    else
        cout << "no target" << endl;

    return 0;
}

Answer 1

修改：

 
#include<iostream>
#include<vector>
using namespace std;
class Solution {
public:
    static int search(vector<int>& arr, int target) {
            if (target<arr[0] || target>*(arr.end() - 1)) //如果目标在超出容器范围就不必寻找
                return -1;
        int left = 0; //头指针
        int right = arr.size(); //尾指针
        while (left < right) {
            int middle = (left + right) >> 1; //中间值
#if 1 //第一个条件语句能够正确输出结果
            if (arr[middle] < target)
                left = middle + 1;
            else if (target < arr[middle])
                right = middle;
            else
                return middle;
#endif
#if 0 //第二个条件语句不能输出正确结果
            if (target < arr[middle])
                right = middle;
            else if (target > arr[middle])
                left = middle + 1;
            else
                return middle;
#endif 
        }
        return -1;
    }
};
int main() {
    vector<int> arr = {-11,-1,2,4,5,7,9,11,34,55,67 };
    for(int v : arr) {
        int index = Solution::search(arr, v);
        if (index != -1)
            cout << "target(" << arr[index] << ") has been found" << endl;
        else
            cout << "no target" << endl;
    }
    for(int v : {-12,6,68}) {
        int index = Solution::search(arr, v);
        if (index != -1)
            cout << "target(" << arr[index] << ") has been found" << endl;
        else
            cout << "no target" << endl;
    }
    return 0;
}

#if 0预处理后根本就不会包含这个指令到#endif指令之间的代码好吧