将数组元素按访问频度递减的顺序存放,请设计并实现一种改进的顺序查找算法,用c语言实现
时间: 2023-06-10 14:05:56 浏览: 89
一种改进的顺序查找算法是使用哈希表来记录数组元素的访问频度,然后对哈希表按照访问频度进行排序,最后按照排序后的顺序遍历数组即可。
以下是使用哈希表和快速排序实现的C语言代码:
```c
#include <stdio.h>
#include <stdlib.h>
#define MAX_SIZE 100
#define HASH_SIZE 10
typedef struct {
int key;
int value;
} HashEntry;
typedef struct {
HashEntry table[HASH_SIZE];
int size;
} HashTable;
void initHashTable(HashTable* hashTable) {
for (int i = 0; i < HASH_SIZE; i++) {
hashTable->table[i].key = -1;
hashTable->table[i].value = 0;
}
hashTable->size = 0;
}
int hash(int key) {
return key % HASH_SIZE;
}
void insert(HashTable* hashTable, int key) {
int index = hash(key);
if (hashTable->table[index].key == -1) {
hashTable->table[index].key = key;
hashTable->table[index].value = 1;
hashTable->size++;
} else {
hashTable->table[index].value++;
}
}
void swap(HashEntry* a, HashEntry* b) {
HashEntry temp = *a;
*a = *b;
*b = temp;
}
int partition(HashEntry* arr, int left, int right) {
int pivot = arr[right].value;
int i = left - 1;
for (int j = left; j < right; j++) {
if (arr[j].value >= pivot) {
i++;
swap(&arr[i], &arr[j]);
}
}
swap(&arr[i + 1], &arr[right]);
return i + 1;
}
void quickSort(HashEntry* arr, int left, int right) {
if (left < right) {
int pivotIndex = partition(arr, left, right);
quickSort(arr, left, pivotIndex - 1);
quickSort(arr, pivotIndex + 1, right);
}
}
void sortByFrequency(HashTable* hashTable, int* arr, int size) {
for (int i = 0; i < size; i++) {
insert(hashTable, arr[i]);
}
quickSort(hashTable->table, 0, hashTable->size - 1);
}
void printArray(int* arr, int size) {
for (int i = 0; i < size; i++) {
printf("%d ", arr[i]);
}
printf("\n");
}
int main() {
int arr[MAX_SIZE] = { 1, 2, 3, 3, 3, 4, 4, 5, 5, 5 };
int size = 10;
HashTable hashTable;
initHashTable(&hashTable);
sortByFrequency(&hashTable, arr, size);
for (int i = 0; i < hashTable.size; i++) {
int key = hashTable.table[i].key;
int value = hashTable.table[i].value;
for (int j = 0; j < value; j++) {
printf("%d ", key);
}
}
printf("\n");
return 0;
}
```
这个算法的时间复杂度为O(nlogn),其中n为数组的大小。
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