最最简单的二分搜索

#include<bits/stdc++.h>
using namespace std;
#define max 1000
typedef pair<int,int>p;
#define INF  1e9+7
#define ll long long
#define eps 1e-6
int main(int argc, char const *argv[])
{
    int a[5]={1,2,5,6,8};
    int k=6;
    int lb=-1,ub=5,mid;
    while(ub-lb>1){
         mid=(ub-lb)/2;
        if (a[mid]>=k)
        {
            ub=mid;
        }
        else{
            lb=mid;
        }
    }
    printf("%d\n",ub );
    return 0;
}