檔案中的記錄排序

你現在有一個檔案，檔案中順序存有N個記錄，R1,R2,...,RN,這些記錄不是有序的，但是你知道一個整數M,這些記錄滿足R1<R2<...<RM以及RM+1<RM+2<...RN.

1,設計一個演算法或編寫一個程式，將檔案中的記錄排序為R1'<R2',<…<,RN',演算法或程式讀取檔案的次數為O(N),不限記憶體使用量，

2,設計一個演算法或編寫一個程式，將檔案中的記錄排序為R1'<R2'<...<RN',演算法或程式讀寫檔案的次數為O(N)，空間複雜度為O(1)，(亦即，你使用的記憶體大小和M,N均無關。) 1.就是兩個有序數組的合并了,時間複雜度確實是O(N)，好說2.第一個限制空間, or 記憶體不夠時就是外部排序了.主要就是讀寫檔案了.

#include <stdio.h>#include <stdlib.h>#define MAX_LEN 10#define M 5#define N 10int process_file1(int A[]){   FILE* fp1 = fopen("record_bak.txt","w");   int i = 0;   int j = M;   char line[MAX_LEN];   while(i<M && j<N)   {     if(A[i]<A[j])      {        sprintf(line, "%d/n", A[i]);        fwrite(line, 1, strlen(line), fp1);        i++;      }      else      {        sprintf(line, "%d/n", A[j]);        fwrite(line, 1, strlen(line), fp1);        j++;      }    }      if(i==M)    {     while(j<N)     {      sprintf(line, "%d/n", A[j]);      fwrite(line, 1, strlen(line), fp1);      j++;     }     }   else if(j==N)    {     while(i<M)     {      sprintf(line, "%d/n", A[i]);      fwrite(line, 1, strlen(line), fp1);      i++;      }    }  fclose(fp1); }int process_file2(){  FILE* fp = NULL;  FILE* fp1 = NULL;  FILE* fp2 = NULL;    char line1[MAX_LEN];  char line2[MAX_LEN];    int num1 = 0;  int num2 = 0;  int flag = 0;    int i = 0;    fp = fopen("record.txt","r");  fp1 = fopen("record_tmp1.txt","w");  fp2 = fopen("record_tmp2.txt","w");    while(fgets(line1, MAX_LEN, fp))   {     printf("line is %s",line1);     if(i<M)        {         printf("%d/n",fwrite(line1, 1, strlen(line1), fp1));         i++;       }      else       {         printf("%d/n",fwrite(line1, 1, strlen(line1), fp2));         i++;       }    }    fclose(fp);   fclose(fp1);   fclose(fp2);     fp = fopen("record.txt","w");   fp1 = fopen("record_tmp1.txt","r");   fp2 = fopen("record_tmp2.txt","r");      fgets(line1, MAX_LEN, fp1);   fgets(line2, MAX_LEN, fp2);   while(1)   {       num1 = atoi(line1);      num2 = atoi(line2);      if(num1 < num2)       {         fwrite(line1, 1, strlen(line1), fp);         if(!fgets(line1, MAX_LEN, fp1))          {           fwrite(line2, 1, strlen(line1), fp);            flag = 1;           break;          }       }       else       {         fwrite(line2, 1, strlen(line2), fp);         if(!fgets(line2, MAX_LEN, fp2))          {           fwrite(line1, 1, strlen(line1), fp);           flag = 2;           break;          }       }     }    if(flag == 1)   {     while(fgets(line2, MAX_LEN, fp2))       fwrite(line2, 1, strlen(line2), fp);    }   else if(flag == 2)   {     while(fgets(line1, MAX_LEN, fp1))       fwrite(line1, 1, strlen(line2), fp);    }   fclose(fp);   fclose(fp1);   fclose(fp2);   remove("record_tmp1.txt");   remove("record_tmp2.txt");} int main(int argc, char *argv[]){  int A[N];  int i = 0;  FILE* fp = NULL;  char line[MAX_LEN];    fp = fopen("record.txt","r");  while(fgets(line, MAX_LEN, fp))   {     A[i] = atoi(line);     i++;    }   fclose(fp);   process_file1(A);  process_file2(A);  system("PAUSE");      return 0;}