1.2查找--二分

//二分
int erfen(int arr[], int k){
	int low=0, high=sizeof(arr)/sizef(int);
	while(low<=high){
		mid = (low+high)/2;
		if( arr[mid]==k ) return mid;
		if( arr[mid]>k )	high = mid-1;
		else	low = mid+1;
	}
	return 0;
}