Dear gnu / g++ programers:
I copy a piece of simple code from c++ book (practical c++ programing) , page 296, chapter Debugging and optimation
with input also according its indicated , increasing in order in numbers.dat (page 289) file
---------------------
eric@eric-laptop:~/practicalCpp$ cat search0.cpp
/**********************************************************************************
* search -- Search a set of numbers. *
* *
* Usage: *
* search *
* you will be asked numbers to lookup *
* *
* Files: *
* numbers.dat -- numbers 1 per line to search *
* (Numbers must be ordered) *
**********************************************************************************/
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <cstdio>
#include <assert.h>
const int MAX_NUMBERS = 1000; // Max numbers in file
const char *const DATA_FILE = "numbers.dat"; // File with numbers
int data[MAX_NUMBERS]; // Array of numbers to search
int max_count; // Number of valid elements indata
int main()
{
std::ifstream in_file; // Input file
int middle; // Middle of our search range
int low, high; // Upper/lower bound
int search; // number to search for
in_file.open(DATA_FILE, std::ios::in);
if (in_file.bad()) {
std::cerr << "Error:Unable to open " << DATA_FILE << '\n';
exit(8);
}
/*
* Read in data
*/
max_count = 0;
while (true) {
char line[30]; // Line from the input file
if (in_file.eof())
break;
in_file.getline(line, sizeof(line));
assert(max_count >= 0);
assert(max_count < sizeof(data)/sizeof(data[0]));
std::sscanf(line, "0", &data[max_count]);
if (data[max_count] == -1)
break;
++max_count;
}
while (true) {
std::cout << "Enter number to search for or -1 to quit:";
std::cin >> search;
if (search == -1)
break;
low = 0;
high = max_count;
while (true) {
//////////
if (low >= high) {
std::cout << "Not found\n";
break;
}
///////////
middle = (low + high) / 2;
assert(middle >= 0);
assert(middle < sizeof(data)/sizeof(data[0]));
if (data[middle] == search) {
std::cout << "Found at index " << middle << '\n';
break;
}
/*
if (low == high) {
std::cout << "Not found\n";
break;
}
*/
assert(middle >= 0);
assert(middle < sizeof(data)/sizeof(data[0]));
if (data[middle] < search)
low = middle + 1;
else
high = middle - 1;
}
}
return (0);
}
eric@eric-laptop:~/practicalCpp$ cat numbers.dat
4
6
14
16
17
eric@eric-laptop:~/practicalCpp$
--------------------------------------------------
but it not only fail to find any numbers in it, like 4, 6, 14,
and
if I input any character non-integer, it response unstop "Enter number to search for or -1 to quit:"
plz help, Eric/* all that chapter talk about gdb is almost not work on my test, for example , print middle
no symbol table is loaded. Use the "file" command */
