CODEWITHSUNDEEP
c++
T.young
T.young

Reputation: 23

Return true while comparing two different double numbers

There are double numbers in the output

344.6
563.4
455.6
10.7
10.6
1

the last two shows 

    [0] 10.000000000000000  double
    [1] 10.000000000000000  double

in the locals variable in visual studio express 2015, and 

repRate[0]==repRate[1]
true

why? I tried use (double) to make sure. The output gives me two different number but repRate[0]==repRate[1] return true.

this is the input.
    5
    1 10 3456
    2 10 5644
    3 10 4566
    4 20 234
    5 20 232

five means you have 5 items, 1 is id code, 10 is the initial number, 3456 is the final number. the reproduce rate is (3456-10)/10 and I need to sort the array using reproduce rate as index.

#include <iostream>
using namespace std;

int main() {

int n;
int a[110][4];
double repRate[110];
//input
cin >> n;
for (int i = 0; i < n;i++) {
    cin >> a[i][0] >> a[i][1] >> a[i][2];
}

//rep rate
for(int i = 0;i < n;i++){
    repRate[i] = (double) ((double)a[i][2]- (double)a[i][1]) / (double)a[i][1];
    cout << repRate[i] << endl;
}

//sort
for (int i = 0;i < n;i++) {
    for (int j = 0;j < n - i-1;j++) {
        int temp[5];
        int rtemp;
        if (repRate[j]>repRate[j+1]) {
            rtemp = repRate[j+1];
            repRate[j + 1] = repRate[j];
            repRate[j] = rtemp;

            for (int k = 0;k < 4;k++) {
                temp[k] = a[j+1][k];
            }
            for (int k = 0;k < 4;k++) {
                a[j+1][k] = a[j][k];
            }
            for (int k = 0;k < 4;k++) {
                a[j][k] = temp[k];
            }
        }
    }
}
int test;
test = repRate[0] == repRate[1];
cout << test;


return 0;
}

Upvotes: 1

Views: 116

Answers (1)

gsamaras
gsamaras

Reputation: 73394

Try setting rtemp to double, since this line:

rtemp = repRate[j+1];

will cut off some accuracy. That should be a warning on your compiler, if not enable warnings!

After that the output is like this:

5
1 10 3456
2 10 5644
3 10 4566
4 20 234
5 20 232
344.6
563.4
455.6
10.7
10.6
0

where 0 is what you want.

Upvotes: 2

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