外部排序 替换选择

《数据结构与算法分析——C语言描述》  第七章

#include <stdio.h>
#include<queue>
#include"fatal.h"
#define M 3//最大的内存
#define N 33//要排序的数字量，1—N

typedef int ElementType;

char name[200];//生成的名字
std::queue<int> notHandleFile;
std::queue<int> nullFile;

char* fileName(char *buf, int i) {
	strcpy(buf, "T");
	char num[5];
	strcat(buf, _itoa(i + 1, num, 10));
	return buf;
}


int RandInt(int i, int j) {
	int temp;
	temp = (int)(i + (1.0*rand() / RAND_MAX)*(j - i));
	return temp;
}

void getRandomInt(int *A, int n) {
	for (int i = 0; i < n; i++) {
		A[i] = i + 1;
	}
	for (int i = 1; i < n; i++) {
		//std::swap(A[i], A[RandInt(0, i)]);      
		int randAdrr = RandInt(0, i);
		int t = A[i];
		A[i] = A[randAdrr];
		A[randAdrr] = t;
	}
}


void writeRandIntToFile() {
	int a[N];
	getRandomInt(a, N);
	FILE *fp = fopen("ta1", "w");
	for (int &i : a)
		fprintf(fp, "%d ", i);
	fclose(fp);
}

#define leftChild(i) (2*(i)+1)  //下标从0开始
void percDown(int *a, int i, int n) {
	int child = leftChild(i);
	int temp;
	for (temp = a[i]; leftChild(i) < n; i = child) {
		child = leftChild(i);
		if (child != n - 1 && a[child] > a[child + 1])
			child++;
		if (temp > a[child])
			a[i] = a[child];
		else
			break;
	}
	a[i] = temp;
}

void buildHeap(int *arr, int n) {
	for (int i = (n - 1 - 1) / 2; i >= 0; i--) {
		percDown(arr, i, n);
	}
}






void insertHeap(int *arr, int &n) {
	int i;
	int X = arr[n];
	n++;
	for (i = n - 1; i > 0 && arr[(i - 1) / 2] > X; i = (i - 1) / 2)//下表为0的时候就是根节点，不用上滤了
		arr[i] = arr[(i - 1) / 2];
	arr[i] = X;
}



int deleteMin(int *arr, int &n) {//n为数量

	int i, child;
	ElementType minElement, lastElement;

	minElement = arr[0];
	lastElement = arr[n - 1];//删除右下的元素  
	n--;
	for (i = 0; i <n; i = child) {
		child = leftChild(i);
		if (child >= n)//这个用于在最底层的时候，获得的儿子是越界的,此时i是上一次迭代的child,child两儿子中的最小值  
			break;
		if (child != n - 1 && arr[child] > arr[child + 1]) {//不一定有两个儿子  
			child++;
		}
		
		if (lastElement > arr[child])
			arr[i] = arr[child];
		else
			break;
	}

	arr[i] = lastElement;
	return minElement;

}




void initRun(char *inputFileName) {
	FILE* readFp = fopen(inputFileName, "r");
	if (readFp == NULL)
		Error("OPEN FILE FAILED");

	int fileNum = 0;//文件数量


	int arr[M];//二叉堆的数组
	int size = 0;//有效数字个数
	int deadSpace = M - 1;//死区下标


	while (size < M && fscanf(readFp, "%d", &arr[size]) == 1) {//读入数字初始化堆
		size++;
	}


	do {
		FILE *writeFile = fopen(fileName(name, fileNum), "w");
		buildHeap(arr, size);
		while (size != 0) {//堆不是空
			int min = deleteMin(arr, size);
			fprintf(writeFile, "%d ", min);
			
			if (fscanf(readFp, "%d", &arr[deadSpace]) == 1) {//输出了一个数，再读取一个数
				
				if (arr[deadSpace]>min) {//放到堆中
					insertHeap(arr, size);//此时size和deadSize是相同的
				}
				else {//放到死区中
					deadSpace--;
				}
			}

		}
		fclose(writeFile);
		notHandleFile.push(fileNum);
		fileNum++;//下一个串
		size = M - 1 - deadSpace;//求死区中元素的数量
		deadSpace = M - 1;//初始化死区下标
		if (size > 0 && size<M) {//当死区元素没填满的时候从右边移动到左边
			for (int i = 0; i < size; i++) {
				arr[i] = arr[i + M - size];
			}
		}
	} while (!feof(readFp));
	nullFile.push(fileNum);

}



void mergeRun(int file1, int file2, int writefile) {
	FILE *readFp1 = fopen(fileName(name, file1),"r");
	FILE *readFp2 = fopen(fileName(name, file2), "r");
	FILE *writeFp = fopen(fileName(name, writefile), "w");
	int a, b;
	int hasNum1 = 0, hasNum2 = 0;
	while ((hasNum1==1||fscanf(readFp1, "%d", &a)==1)&& (hasNum2 == 1 || fscanf(readFp2, "%d", &b) == 1)) {
		hasNum1 = 1;
		hasNum2 = 1;
		if (a < b) {
			fprintf(writeFp, "%d ", a);
			hasNum1 = 0;
		}
		else {
			fprintf(writeFp, "%d ", b);
			hasNum2 = 0;
		}
	}
	while ((hasNum1 == 1 || fscanf(readFp1, "%d", &a) == 1)) {
			fprintf(writeFp, "%d ", a);
			hasNum1 = 0;
	}
	while (hasNum2 == 1 || fscanf(readFp2, "%d", &b) == 1) {
			fprintf(writeFp, "%d ", b);
			hasNum2 = 0;
	}
	fclose(readFp1);
	fclose(readFp2);
	fclose(writeFp);
}




int main() {
	writeRandIntToFile();
	char inputFileName[20] = "ta1";//要排序的文件
	//scanf("%s", inputFileName);
	initRun(inputFileName);//初始化顺序串

	int cnt = 0;
	while (notHandleFile.size() > 1) {
		
		int file1 = notHandleFile.front();
		notHandleFile.pop();
		int file2 = notHandleFile.front();
		notHandleFile.pop();
		int writeFile = nullFile.front();
		nullFile.pop();
		mergeRun(file1, file2, writeFile);
		nullFile.push(file1);
		nullFile.push(file2);
		notHandleFile.push(writeFile);
		
	}
}