class Solution {
    public int largestAltitude(int[] gain) {
        int res = 0;
        int high = 0;
        for (int i : gain) {
            high += i;
            res = Math.max(high,res);
        }
        return res;
    }
}

class Solution {
    int num = 0;
	int res;
	public int kthSmallest(TreeNode root, int k) {
		if(root.left != null) {
			kthSmallest(root.left, k);
		}
		num++;
		if(num == k) res = root.val;
		if(root.right != null) {
			kthSmallest(root.right, k);
		}
		return res;
    }
}

class Solution {
    public int pivotIndex(int[] nums) {
        int len = nums.length;
        int sum = 0;
        for(int num : nums) sum += num;
        int mid = 0;
        int left = 0;
        for(;mid<len;mid++){
            left+=nums[mid];
            if(left == sum - left + nums[mid]){
                return mid;
            }
        }
        return -1;
    }
}