二分搜索

// CodeForces 600B
//二分搜索 时间复杂度为O(log n)
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<ctype.h>
#include<math.h>
#include<algorithm>
using namespace std;

#define N 200100
#define INF 0x3f3f3f3f

int a[N], b[N];

int main()
{
    int n, m;
    scanf("%d%d", &n, &m);

    for(int i=0; i<n; i++)
        scanf("%d", &a[i]);
    for(int i=0; i<m; i++)
        scanf("%d", &b[i]);
    sort(a, a+n);

    for(int i=0; i<m; i++)
    {
        int left, right, mid=-1;
        left=0, right=n-1;

        while(left<=right)
        {
            mid=(left+right)/2;
            if(a[mid]>b[i])
            {
                if(a[mid-1] <= b[i]) break;
                right=mid-1;
            }
            else if(a[mid]<=b[i])
            {
                if(mid == n-1)
                {
                    mid ++;break;
                }
                left=mid+1;
            }

        }
        printf("%d%c", mid, i==m-1 ? ‘\n‘ : ‘ ‘);
    }

    return 0;
}