题目：

题解：

type Solution struct {pre []int
}func Constructor(w []int) Solution {for i := 1; i < len(w); i++ {w[i] += w[i-1]}return Solution{w}
}func (s *Solution) PickIndex() int {x := rand.Intn(s.pre[len(s.pre)-1]) + 1return sort.SearchInts(s.pre, x)
}