在兩個長度相等的排序數組中找到中位數

/*public class Main{
	public static int getUpMedia(int[] arr1,int[] arr2) {
		if(arr1 == null || arr2 == null) {
			return -1;
		}
		else {
			return find(arr1,0,arr1.length-1,arr2,0,arr2.length-1);
		}
	}
	public static int find(int[] arr1,int l1,int r1,int[] arr2,int l2,int r2) {
		int mid1 = l1 + (r1 - l1) / 2;
		int mid2 = l2 + (r2 - l2) / 2;
		if(l1 >= r1) {
			return Math.min(arr1[l1], arr2[l2]);
		}
		//元素個數為奇數，則offset=0，反之為1
		int len = r1 - l1 +1;
		int offset = 0;
		if(len % 2 == 0) {
			offset = 1;
		}
		if(arr1[mid1] < arr2[mid2]) {
			return find(arr1,mid1+offset,r1,arr2,l2,mid2);
		}else if(arr1[mid1] > arr2[mid2]){
			return find(arr1,l1,mid1,arr2,mid2+offset,r2);
		}else {
			return arr1[mid1];
		}
	}
	public static void main(String[] args) {
		
	}
}*/
public static int getUpMedia(int[] arr1,int[] arr2) {
	if(arr1 == null || arr2 == null) {
		return -1;
	}
	int l1 = 0;
	int r1 = arr1.length - 1;
	int l2 = 0;
	int r2 = arr2.length - 1;
	int mid1 = 0;
	int mid2 = 0;
	int offset = 0;
	while(l1 < r1) {
		mid1 = l1 + (r1 - l1) / 2;
		mid2 = l2 + (r2 - l2) / 2;
		
	    int len  = r1 - l1 + 1;
	    if(len % 2 == 0) {
	    	offset = 1;
	    }
	    if(arr1[mid1] < arr2[mid2]) {
	    	l1 = mid1 + offset;
	    	r2 = mid2;
	    }else if(arr1[min1] > arr2[mid2]) {
	    	r1 = mid1;
	    	l2 = mid2 + offset;
	    }else {
	    	return arr2[mid1];
	    }
	
	}
	return Math.min(arr1[l1],arr2[l2]);
}