Check if an array is sorted, return true or false

Question

I am writing an easy program the just returns true if an array is sorted else false and I keep getting an exception in eclipse and I just can\'t figure out why. I was wonder

Answer 1

You shouldn't use a[i+1] because that value may or may not go off the array.

For example:

A = {1, 2, 3}
// A.length is 3.
for(i = 0; i < a.length; i ++) // A goes up to 3, so A[i+1] = A[4]

To fix this, simply stop the loop one early.

int i;
for(i = 0; i < a.length - 1; i ++);{

    if (a[i] < a[i+1]) {

        return true;
    }else{
        return false;

    }

}

Answer 2

Array.prototype.every

The every() method tests whether all elements in the array pass the test implemented by the provided function.

arr.every(function (a, b) {
  return a > b;
});

var arr = [1,2,3] // true

var arr = [3,2,1] // false

Answer 3

For anyone using Java 8 and above, here's a simple one-liner:

public static boolean isSorted(int[] array) {
    return IntStream.range(0, array.length - 1).noneMatch(i -> array[i] > array[i + 1]);
}

Or a logically-equivalent alternative:

public static boolean isSorted(int[] array) {
    return IntStream.range(0, array.length - 1).allMatch(i -> array[i] <= array[i + 1]);
}

Answer 4

bool checkSorted(int a[], int n) {
  for (int i = 1; i < n-1; i++) {
    if (a[i] > a[i-1]) {
      return false;
    }
  }
  return true;
}

Answer 5

public static boolean isSorted(int[] a)
{  
    for ( int i = 0; i < a.length - 1 ; i++ ) {
        if ( a[i] > a[i+1] )
          return false;
    }
    return true;
}

This function checks whether the array is in Ascending order or not.

Answer 6

boolean checkElements(int arr[],  int first, int last) {
    while(arr.length > first) {
        if(arr[i] > arr[last-1]) {
            if(arr[i] > arr[i+1])
                return checkElements(arr, first+1, first+2);;
            return false;
        }else {
            if(arr[i] < arr[i+1])
                return checkElements(arr, first+1, first+2);
            return false;
        }
    }
    return true;
}