数组子元素之和问题

题目：给定一个数组和一个数字，判断数组中是否有子元素之和为该数字。如数组{3，5，7，9}，给出数字6，返回False,给出数字8，返回True.

递归方式：

int IsFit(vector<int> arr,int sum,int i) {
	if (sum == 0)
		return true;
	else if (arr[i] == sum) return true;
	else if (i == 0) return false;
	else if (arr[i] > sum) return IsFit(arr, sum, i - 1);
	else
	{
		return IsFit(arr, sum, i - 1) || IsFit(arr, sum - arr[i], i - 1);
	}

}

非递归方式：

int NoRec_IsFit(vector<int> arr, int sum) {
	bool **status = new bool*[arr.size()];
	for (int i = 0;i < arr.size();i++) status[i] = new bool[sum+1];
	for (int i = 1;i <=sum;i++) { status[0][i] = false; }
	status[0][arr[0]] = true;
	for (int i = 0;i < arr.size();i++) status[i][0] = true;
	for (int i = 1;i < arr.size();i++) {
		for (int j = 1;j <= sum;j++) {
			if (arr[i] > j) status[i][j] = status[i - 1][j];
			else if((j-arr[i])>sum)status[i][j] = status[i-1][j];
			else status[i][j] = status[i - 1][j] || status[i - 1][j - arr[i]];
		}
	}
	int res = status[arr.size() - 1][sum];
	//删除申请的内存
	for (int i = 0;i < arr.size();i++) delete[] status[i];
	delete[] status;
	return res;
}