55 lines
1.6 KiB
C++
55 lines
1.6 KiB
C++
// Source : https://leetcode.com/problems/random-pick-index/
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// Author : Hao Chen
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// Date : 2016-11-04
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/***************************************************************************************
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*
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* Given an array of integers with possible duplicates, randomly output the index of a
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* given target number. You can assume that the given target number must exist in the
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* array.
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*
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* Note:
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* The array size can be very large. Solution that uses too much extra space will not
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* pass the judge.
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*
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* Example:
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*
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* int[] nums = new int[] {1,2,3,3,3};
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* Solution solution = new Solution(nums);
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*
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* // pick(3) should return either index 2, 3, or 4 randomly. Each index should have
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* equal probability of returning.
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* solution.pick(3);
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*
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* // pick(1) should return 0. Since in the array only nums[0] is equal to 1.
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* solution.pick(1);
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***************************************************************************************/
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class Solution {
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private:
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vector<int> nums;
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public:
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Solution(vector<int> nums) {
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srand(time(0));
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this->nums = nums;
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}
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int pick(int target) {
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// we just randomly pick a number from the array,
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// if the number is target just return the index.
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// otherwise, keep picking the number randomly.
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while(true) {
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int idx = rand() % nums.size();
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if ( target == nums[idx] ) {
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return idx;
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}
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}
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}
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};
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/**
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* Your Solution object will be instantiated and called as such:
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* Solution obj = new Solution(nums);
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* int param_1 = obj.pick(target);
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*/
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