package main

import (
	"fmt"
	"sort"
)

func triangleNumber(nums []int) (res int) {
	sort.Ints(nums)
	n := len(nums)
	trace := make([]int, 0, 0)
	var backtrace func(idx int) bool
	backtrace = func(idx int) bool {
		fmt.Println(trace)
		if len(trace) == 3 {
			if trace[0]+trace[1] > trace[2] {
				res++
				return true
			}
			return false
		}
		for i := idx; i < n; i++ {
			trace = append(trace, nums[i])
			flag := backtrace(i + 1)
			trace = trace[:len(trace)-1]
			if !flag {
				break
			}
		}
		return true
	}
	backtrace(0)
	return res
}