统计一个数字在排序数组中出现的次数（二分法)

#include<iostream>
#include<algorithm>
#include<stdio.h>
using namespace std;
int a[500001];
int binarySearchFirstPos(int l, int r, int key)
{
	int mid;
    while(l<=r){
	mid =(l+r)/2;
	if(a[mid]<key)
		l=mid+1;
	else if(a[mid]>key)
		r=mid-1;
	else {
	if(mid==l||a[mid-1]!=key)
		return mid;
	else r=mid-1;
	}
	}
	return -1;
}
int binarySearchLastPos(int l, int r, int key)
{
	int mid;
    while(l<=r){
	mid =(l+r)/2;
	if(a[mid]<key)
		l=mid+1;
	else if(a[mid]>key)
		r=mid-1;
	else {
	if(mid==r||a[mid+1]!=key)
		return mid;
	else l=mid+1;
	}
	}
	return -1;
}
int numOfKey(int l,int r, int key)
{
    int firstPos = binarySearchFirstPos(l,r, key);
    int lastPos = binarySearchLastPos(l,r, key);
    
    if(firstPos == -1)
        return 0;
    else
        return lastPos - firstPos + 1;
}
int main(){
	int n,m,i;
	scanf("%d%d",&n,&m);
	for(i=1;i<=n;i++)
		scanf("%d",&a[i]);
	sort(a+1,a+n+1);
	int tem;
	for(i=1;i<=m;i++)
	{
		scanf("%d",&tem);
		cout<<numOfKey(1,n,tem)<<endl;
	}

}

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