Why doesn't setting variables equal to an array index work in the expected way?

Question

Two versions of very similar code... one works, the other doesn't...

Array Used:

int[] input = new int[10];

//

for(int i = 0; i < input.length; i++) {
                //int inputi = input[i];
            for(int j = 0; j < input.length; j++) {
                //int inputj = input[j];
                if(input[i] < input[j]) {
                      input[j] = input[i];
                      min = input[j];
                  }
            }

The code above works. The code below doesn't, what gives?

for(int i = 0; i < input.length; i++) {
                int inputi = input[i];
            for(int j = 0; j < input.length; j++) {
                int inputj = input[j];
                if(inputi < inputj) {
                      inputj = inputi;
                      min = inputj;
                  }
            }

Shouldn't it do the exact same thing? The first code returns the minimum value, the second does not.

Sorry for the possibly confusing variable names, I only chose those so I could easily switch back and forth.

Foo Bah · Accepted Answer · 2011-02-02 05:51:14Z

3

the assignment is broken: inputj and inputi are temporary variables.

                  inputj = inputi;

changes temporary variable

                  input[j] = input[i];

actually changes the array values.

just to get the min value:

min = input[0];
for(int i = 1; i < input.length; i++) {
            if(min > input[i]) {
                  min = input[i];
            }
}

answered Feb 2, 2011 at 5:51

Foo Bah

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6 Comments

Hanna Over a year ago

How can I grab the right value without reassigning the array value?

Foo Bah Over a year ago

if you just want the minimum value, you can do a single pass

Hanna Over a year ago

@Foo Bah: Do you think you could explain what that means? I'm sorry, I'm still learning so much.

Foo Bah Over a year ago

if you want te sorted array, you either need to copy the array [external sorting] or manipulate the array

Foo Bah Over a year ago

if you only want to find the minimum value, the code in my response will compute the minimum. If you want to actually sort the result, your first code block is almost correct (instead of just assigning, you should swap input[i] and input[j])

|

Justin Morgan · Accepted Answer · 2011-02-02 05:57:12Z

1

Are you just trying to get the minimum value of the array?

int min = input[0];
for (int i = 0; i < input.length; i++) {
  if (input[i] < min) {
    min = input[i];
  }
}

answered Feb 2, 2011 at 5:57

Justin Morgan

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