Solution.java

import java.util.Arrays;

public class Solution
{
    public int triangleNumber(int[] nums)
    {
        if (nums == null || nums.length < 3)
        {
            return 0;
        }
        int count = 0;
        int n = nums.length;
        Arrays.sort(nums);
        for (int i = 2; i < n; i++)
        {
            int a = nums[i];
            int l = 0;
            int r = i - 1;
            while (l < r)
            {
                int b = nums[l];
                int c = nums[r];
                int sum = b + c;
                if (sum > a)
                {
                    count += (r - l);
                    r--;
                }
                else
                {
                    l++;
                }
            }
        }
        return count;
    }
}