398. Random Pick Index
Description
Given an integer array nums
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.
Implement the Solution
class:
Solution(int[] nums)
Initializes the object with the arraynums
.int pick(int target)
Picks a random indexi
fromnums
wherenums[i] == target
. If there are multiple valid i's, then each index should have an equal probability of returning.
Example 1:
Input ["Solution", "pick", "pick", "pick"] [[[1, 2, 3, 3, 3]], [3], [1], [3]] Output [null, 4, 0, 2] Explanation Solution solution = new Solution([1, 2, 3, 3, 3]); solution.pick(3); // It should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning. solution.pick(1); // It should return 0. Since in the array only nums[0] is equal to 1. solution.pick(3); // It should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning.
Constraints:
1 <= nums.length <= 2 * 104
-231 <= nums[i] <= 231 - 1
target
is an integer fromnums
.- At most
104
calls will be made topick
.
Solutions
Solution 1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 |
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 |
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 |
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 |
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