42 lines
1.1 KiB
C++
42 lines
1.1 KiB
C++
// Source : https://leetcode.com/problems/elimination-game
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// Author : Hao Chen
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// Date : 2016-09-07-
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/**********************************************************************************
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*
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* There is a list of sorted integers from 1 to n. Starting from left to right, remove the first number and every other
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* number afterward until you reach the end of the list.
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*
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* Repeat the previous step again, but this time from right to left, remove the right most number and every other number
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* from the remaining numbers.
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*
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* We keep repeating the steps again, alternating left to right and right to left, until a single number remains.
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*
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* Find the last number that remains starting with a list of length n.
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*
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* Example:
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*
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* Input:
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* n = 9,
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* 1 2 3 4 5 6 7 8 9
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* 2 4 6 8
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* 2 6
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* 6
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*
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* Output:
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* 6
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**********************************************************************************/
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class Solution {
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public:
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int lastRemaining(int n) {
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int start = 1, step = 1;
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while (n > 1) {
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start += step + (n-2)/2 * 2*step;
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n /= 2;
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step *= -2;
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}
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return start;
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}
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};
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