本文實例講述了C++實現查找中位數的O(N)算法和Kmin算法，分享給大家供大家參考。具體方法如下：
利用快速排序的partition操作來完成O(N)時間內的中位數的查找算法如下：
#include <iostream>#include <cassert>#include <algorithm>#include <iterator>using namespace std;int array[] = {1, 2, 10, 8, 9, 7, 5};const int size = sizeof array / sizeof *array;int partition(int *array, int left, int right){ if (array == NULL) return -1; int pos = right; right--; while (left <= right) { while (left < pos && array[left] <= array[pos]) left++; while (right >= 0 && array[right] > array[pos]) right--; if (left >= right) break; swap(array[left], array[right]); } swap(array[left], array[pos]); return left;}int getMidIndex(int *array, int size){ if (array == NULL || size <= 0) return -1; int left = 0; int right = size - 1; int midPos = right >> 1; int index = -1; while (index != midPos) { index = partition(array, left, right); if (index < midPos) { left = index + 1; } else if (index > midPos) { right = index - 1; } else { break; } } assert(index == midPos); return array[index];}void main(){ int value = getMidIndex(array, size); cout << "value: " << value << endl;}尋找kmin算法如下：
int findKMin(int *array, int size, int k){ if (array == NULL || size <= 0) return -1; int left = 0; int right = size - 1; int index = -1; while (index != k) { index = partition(array, left, right); if (index < k) { left = index + 1; } else if (index > k) { right = index - 1; } else { break; } } assert(index == k); return array[index];}希望本文所述對大家C++程序算法設計的學習有所幫助。
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