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Given an array of integers with possible duplicates, randomly output the index of a given target number. You can assume that the given target number must exist in the array.
Note:
The array size can be very large. Solution that uses too much extra space will not pass the judge.Example:
int[] nums = new int[] {1,2,3,3,3};Solution solution = new Solution(nums);// pick(3) should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning.solution.pick(3);// pick(1) should return 0. Since in the array only nums[0] is equal to 1.solution.pick(1); Accepted
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并不是很喜欢这题的表述，这题的意思应该是说不要对输入nums进行任何操作，或者说nums是个stream，这样用蓄水池算法理所当然，否则每次都遍历一遍有点牵强
import randomclass Solution: def __init__(self, nums): self.nums = nums def pick(self, target): cnt,res = 0,0 for i,num in enumerate(self.nums): if (num == target): cnt += 1 if (cnt == 1): res = i else: rdint = random.randint(1, cnt) if (rdint == 1): res = i return res# Your Solution object will be instantiated and called as such:# obj = Solution(nums)# param_1 = obj.pick(target)
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