题目：

题解：

func numberOfArithmeticSlices(nums []int) (ans int) {f := make([]map[int]int, len(nums))for i, x := range nums {f[i] = map[int]int{}for j, y := range nums[:i] {d := x - ycnt := f[j][d]ans += cntf[i][d] += cnt + 1}}return
}