二分模版之一

#include <iostream>

using namespace std;

int main() {
    int arr[5] = {1,2,3,5,6};
    int l = 0,r = 5-1;
    int target = 5;
    while (l<r) {
        int mid = l + r >> 1;//大于等于目标向下取整 小于等于目标向上取整
        if (arr[mid] >= target) { 
            r = mid; // 等于和等于放一起
        } else {
            l = mid+1;
        }
    }
    cout << l << endl;
}