HDU 1003 WA，测试好多数据，包括全负数的输入，请问大家还有哪里有错？

[no_sure]

#include "iostream"
#include "vector"
using namespace std;
int maxSubSum(const vector<int> & a,int & beg, int & end){
	int maxSum = INT_MIN;
 	int size =a.size();
	for(int i = 0;i < size;i++ ){
		int thisSum=0;
		for(int j = i;j <size; j++){
			thisSum+=a[j];
			if (thisSum > maxSum ){
				maxSum = thisSum;
				beg = i;
				end = j;
			}
			
		}
		return maxSum;
	}
}
int main(){
	int cases;
	cin>>cases;
	for(int i=0; i < cases; i++){
		int nums;
		cin>> nums;
		vector<int> ivec;
		ivec.clear();
		for(int j=0; j<nums; j++){
			int num;
			
			cin>> num;
			ivec.push_back(num);	
		}
		int beg=0,end=0,maxresult;
		maxresult= maxSubSum(ivec,beg,end);
		cout<<"Case "<<i+1<<":"<<endl;
		cout<<maxresult<<" "<<beg+1<<" "<<end+1<<endl;
		if(cases!=1 && (i+1)!=cases)
		cout<<endl;
	}
	

return 0;	
}

[shi3590]

maxSubSum在干吗？
看似两层循环，实际在做了一次循环之后就return回去了。