在我的数组循环中找不到正确的最大值

Question

So my professor gave us this project to read a text file and find the max value, min value, sum. But for some reason when I write the for loop to find the max value it returns a number thats not even in the text file... and I don't know what i did wrong. I'll attach my code and also the output. Thank you

int main () {

ifstream myFile;
char myArray[210];
int i;
int maxVal;
int j;
int minValue;
double myAverage;


myFile.open("Lab #5A Data File.Txt", ios::in | ios::out);

if (myFile.is_open()) {
    cout << "The file is open." << endl; 

    myFile >> noskipws;

while (!myFile.eof()){


for (i=0; i<210; ++i) {


    myFile >> myArray[i];
    cout << myArray[i];
     } 
     myFile >>myArray[i];

    }

maxVal=myArray[0];

for (j=0; j< 210; j++)
    if (myArray[j] > maxVal){

        maxVal=myArray[j];
    }

What i get when I run the code :

The file is open.

346 130 982 90 656 117 595 415 948 126 4 558 571 87 42 360 412 721 463 47 119 441 190 985 214 509 2 571 77 81 681 651 995 93 74 310 9 995 561 92 14 288 466 664 892 8 766 34 639 151 64 98 813 67 834 369

The max value is: 51 <--- I have no idea where this number came from...

Answer 1

The 51 is coming from the line:

maxVal=myArray[0];

In your loop to try to find the biggest element you have:

for (j=0; j< 210; j++)
    if (myArray[j] > maxVal){
        myArray[i]=maxVal;
    }
}

However this will assign maxVal to myArray[i] which is not what you want. First of all you need to be assigning myArray[j] , not myArray[i] , and secondly you need to assign maxVal to the bigger value. As it is maxVal=myArray[0]; is the only time you assign anything to maxVal , which is why it is 51 (The ASCII value of the character 3 , which is the first character you read). You need to do something along the lines of:

if (myArray[j] > maxVal){
     maxVal = myArray[j];
}

I believe you wanted myArray to be an int[] . Also a better way of doing this is instead of having two for loops and looping until EOF, loop while myFile >> myArray[i] :

int myArray[210];
int i = 0;
//...
while (myFile >> myArray[i]) {          
    cout << myArray[i] << " ";  
    if (myArray[i] > maxVal) {
        maxVal = myArray[i];
    }
    i++;
}   

Which for the input file:

346 130 982 90 656 117 595 
415 948 126 4 558 571 87 42 
360 412 721 463 47 119 441 
190 985 214 509 2 571 77 81 
681 651 995 93 74 310 9 995 
561 92 14 288 466 664 892 8 
766 34 639 151 64 98 813 67 834 369

Returns:

995

Answer 2

To achieve what you want, you cannot do a comparison like this

if (myArray[j] > maxVal){

because myArray[j] is a char (definitely not holding the integers you are interested in) and maxVal is an int. This is also the reason you see a 51 - when you try to store an integer into your char, you essentially only read 8 bits from the stream (which results in some value between 0 and 254 which is basically just some 8-bit block from your input stream).

You definitely want something like

char myArray[32][210]; 

to be able to read your full integers from the stream into one of these 210 char* slots. Then, when comparing (and assigning to maxValue), you need to convert the textual int value to a numeric value, eg, using atoi().