アルゴリズムとデータ構造：ソート、サーチの数値以外への応用

ここまでに出て来たソート、サーチのプログラムは全て数値のみを対象として
操作されていたが、もちろん配列でも同じように書けるよ的な応用。
本の検索がお題。

[book_seach.c]

#include <stdio.h>
#include <stdlib.h>

#define N 5

typedef struct {
    char *title;
    char *author;
    int bookID;
    int available;
} book;

book *bookarray[N];

void initdata(void){
    int n;
    for(n = 0; n < N; n++){
         bookarray[n] = (book*)malloc(sizeof(book));
    }

    bookarray[0]->title = "book0";
    bookarray[1]->title = "book1";
    bookarray[2]->title = "book2";
    bookarray[3]->title = "book3";
    bookarray[4]->title = "book4";
    bookarray[0]->author = "author0";
    bookarray[1]->author = "author1";
    bookarray[2]->author = "author2";
    bookarray[3]->author = "author3";
    bookarray[4]->author = "author4";
    bookarray[0]->bookID = 1000;
    bookarray[1]->bookID = 502;
    bookarray[2]->bookID = 731;
    bookarray[3]->bookID = 628;
    bookarray[4]->bookID = 1;
    bookarray[0]->available = 1;
    bookarray[1]->available = 0;
    bookarray[2]->available = 0;
    bookarray[3]->available = 1;
    bookarray[4]->available = 1;
}

void cleanupdata(void){
   int n; 
   for (n = 0; n < N; n++) {
        free(bookarray[n]); 
   }
}

void sortbook(int bottom, int top){
    int lower, upper, div;
    book *temp;

    if (bottom >= top) {
        return; 
    }

    div = bookarray[bottom]->bookID;
    for (lower = bottom, upper = top; lower < upper;) {
        while (/*lower < upper && */ bookarray[lower]->bookID < div) {
            lower++; 
        }
        while (/*lower < upper && */ bookarray[upper]->bookID > div) {
            upper--; 
        }
        if (lower < upper) {
            temp = bookarray[lower]; 
            bookarray[lower] = bookarray[upper];
            bookarray[upper] = temp;
            lower++;
            upper--;
        }
        sortbook(bottom, upper);
        sortbook(upper + 1, top);
    }
}

int searchbook(book *books[],int size, int key){
    int left, mid, right;
    left = 0;
    right = size;
    while (left < right) {
        mid = (left + right)  / 2;
        if (books[mid]->bookID < key){
            left = mid + 1; 
        }
        else {
            right = mid; 
        }
    }
    if (books[left]->bookID == key) {
        return left; 
    }

    return -1;
}

int main(void) {
    int key, position;

    initdata();
    sortbook(0, N - 1);

    while (1) {
        printf("検索する本の番号を入力"
        "(0で終了)："); 
        scanf("%d", &key);
        if (key == 0) break;

        position = searchbook(bookarray, N - 1, key);
        if (position != -1) {
            printf("-- 次の本が見つかりました --\n"
                    "[タイトル]%s [著者]%s [管理番号]%d \n", 
                    bookarray[position]->title,
                    bookarray[position]->author,
                    bookarray[position]->bookID
                    ); 
            if (bookarray[position]->available != 0) {
                puts("この本は貸し出し可能です\n"); 
            }
            else {
                puts("この本は貸し出し中です\n"); 
            }
        }
        else {
            puts("お探しの本は見つかりませんでした\n"); 
        }
    }
    cleanupdata();
    return 0;
}

ちょっとしか変わらないけどC++版。
C++に全くわかりませんが演算子のオーバーロードってよくあるの？
個人的には好きじゃないけど、世間では当たり前でしょ、って感じだったら慣れようか。
[book_seach.cpp]

#include <stdio.h>
#include <stdlib.h>

class CBook {
public:
    char *title;
    char *author;
    int bookID;
    int available;

    bool operator<(CBook& book) {
        return bookID < book.bookID; 
    }
    bool operator>(CBook& book) {
        return bookID > book.bookID; 
    }
    operator int() {
        return bookID; 
    }
};

#define N 5

CBook *bookarray[N];

void initdata(void){
    int n;
    for(n = 0; n < N; n++){
         //bookarray[n] = (book*)malloc(sizeof(book));
         bookarray[n] = new CBook;
    }

    bookarray[0]->title = "book0";
    bookarray[1]->title = "book1";
    bookarray[2]->title = "book2";
    bookarray[3]->title = "book3";
    bookarray[4]->title = "book4";
    bookarray[0]->author = "author0";
    bookarray[1]->author = "author1";
    bookarray[2]->author = "author2";
    bookarray[3]->author = "author3";
    bookarray[4]->author = "author4";
    bookarray[0]->bookID = 1000;
    bookarray[1]->bookID = 502;
    bookarray[2]->bookID = 731;
    bookarray[3]->bookID = 628;
    bookarray[4]->bookID = 1;
    bookarray[0]->available = 1;
    bookarray[1]->available = 0;
    bookarray[2]->available = 0;
    bookarray[3]->available = 1;
    bookarray[4]->available = 1;
}

void cleanupdata(void){
   int n; 
   for (n = 0; n < N; n++) {
        delete bookarray[n]; 
   }
}

void sortbook(int bottom, int top){
    int lower, upper;
    CBook *div, *temp;

    if (bottom >= top) {
        return; 
    }

    div = bookarray[bottom];
    for (lower = bottom, upper = top; lower < upper;) {
        while (*bookarray[lower] < *div) {
            lower++; 
        }
        while (*bookarray[upper] > *div) {
            upper--; 
        }
        if (lower < upper) {
            temp = bookarray[lower]; 
            bookarray[lower] = bookarray[upper];
            bookarray[upper] = temp;
            lower++;
            upper--;
        }
        sortbook(bottom, upper);
        sortbook(upper + 1, top);
    }
}

int searchbook(CBook *books[],int size, int key){
    int left, mid, right;
    left = 0;
    right = size;
    while (left < right) {
        mid = (left + right)  / 2;
        if (*books[mid] < key){
            left = mid + 1; 
        }
        else {
            right = mid; 
        }
    }
    if (*books[left] == key) {
        return left; 
    }

    return -1;
}

int main(void) {
    int key, position;

    initdata();
    sortbook(0, N - 1);

    while (1) {
        printf("検索する本の番号を入力"
        "(0で終了)："); 
        scanf("%d", &key);
        if (key == 0) break;

        position = searchbook(bookarray, N - 1, key);
        if (position != -1) {
            printf("-- 次の本が見つかりました --\n"
                    "[タイトル]%s [著者]%s [管理番号]%d \n", 
                    bookarray[position]->title,
                    bookarray[position]->author,
                    bookarray[position]->bookID
                    ); 
            if (bookarray[position]->available != 0) {
                puts("この本は貸し出し可能です\n"); 
            }
            else {
                puts("この本は貸し出し中です\n"); 
            }
        }
        else {
            puts("お探しの本は見つかりませんでした\n"); 
        }
    }
    cleanupdata();
    return 0;
}