leetcode-go/medium/398.random-pick-index.go

type Solution struct {
	index map[int][]int
}

func Constructor(nums []int) Solution {
	sol := Solution{index: make(map[int][]int)}
	for i, n := range nums {
		sol.index[n] = append(sol.index[n], i)
	}
	return sol
}

func (this *Solution) Pick(target int) int {
	arr := this.index[target]
	return arr[rand.Intn(len(arr))]
}

/**
 * Your Solution object will be instantiated and called as such:
 * obj := Constructor(nums);
 * param_1 := obj.Pick(target);
 */