寻找第K大的数

#include <stdio.h>#include <stdlib.h>int Left(int parent) {  return parent * 2 + 1;}int Right(int parent) {  return (parent + 1) * 2;}int Parent(int child) {  return (child - 1) / 2;}template<typename T>void Swap(T& left, T& right) {  T tmp = left;  left = right;  right = tmp;}template<typename T>void MinHeapfy(T array[], int parent, int length) {  int min = parent;    if (Left(parent) < length && array[Left(parent)] < array[parent]) {    min = Left(parent);  }  if (Right(parent) < length && array[Right(parent)] < array[min]) {    min = Right(parent);  }  if (min != parent) {    Swap(array[parent], array[min]);    MinHeapfy(array, min, length);  }}template<typename T>bool HeapFinding(T array[], const T& target, int parent, int length) {  bool left_match = Left(parent) < length && target == array[Left(parent)];  bool right_match = Right(parent) < length && target == array[Right(parent)];  if (left_match || right_match) {    return true;  }  bool left_finded, right_finded;  if (Left(parent) < length && array[Left(parent)] < target) {    left_finded = HeapFinding(array, target, Left(parent), length);  } else {    left_finded = false;  }  if (Right(parent) < length && array[Right(parent)] < target) {    right_finded = HeapFinding(array, target, Right(parent), length);  } else {    right_finded = false;  }  if (left_finded || right_finded) {    return true;  } else {    return false;  }}template<typename T>T FindMaxK(T array[], int start, int end, int K) {  if (K > 0) {    int middle = (start + end) / 2;    T average = (array[start] + array[middle] + array[end]) / 3;    //    printf("%d\n", average);    int j = start - 1;    for (int i = start; i <= end; ++i) {      if (array[i] <= average) {        Swap(array[i], array[j + 1]);        j++;      }    }    int length = end - (j + 1) + 1;    if (length > K) {      return FindMaxK(array, j + 1, end, K);    } else if(length == K) {      return array[j + 1];    } else {      return FindMaxK(array, start, j, K - length);    }  } }  int main(int argc, char** argv) {  const int kDataSize = 100;  int array[kDataSize];  for (int i = 0; i < kDataSize; ++i) {    array[i] = rand() % 10;    printf("%d\n", array[i]);  }  const int heap_size = 3;  int heap[heap_size] = {0x80000001, 0x80000001,0x80000001};  for (int i = 0; i < kDataSize; ++i) {    if (array[i] > heap[0]) {      if (!HeapFinding(heap, array[i], 0, heap_size)) {        heap[0] = array[i];        MinHeapfy(heap, 0, heap_size);      }    }    /*    for (int i = 0; i < heap_size; ++i) {      printf("%d ", heap[i]);    }    printf("\n");    */  }  for (int i = 0; i < heap_size; ++i) {    printf("%d ", heap[i]);  }  printf("\n");  printf("max Kth = %d\n", FindMaxK(array, 0, kDataSize -1, 1));}

参考文献：

编程之美2.5

http://www.cnblogs.com/jillzhang/archive/2007/10/04/913478.html