v0.40: Create exercises. Challenge the community.

unique_sorted

Your mission

Write a function that squeezes the duplicates out of an already sorted array in place and returns how many distinct values it kept.

See it in action

int a[] = {1, 1, 2, 3, 3, 3}; unique_sorted(a, 6);

Expected result

3 | 1 2 3

Your checklist

For your own tracking. Tests grade your code.

a points to n integers already sorted in ascending order. Rely on it: two equal values are always neighbours.
Move the distinct values to the front of a, in the same order, so the caller reads them in a[0] through a[ret - 1].
Return the number of distinct values.
Indices from ret up to n - 1 are unspecified. Leave anything you want there, the tests read the prefix [0, ret) and nothing else.
When n is 0, return 0 and read nothing.
Work in place: no allocation and no library call.
The examples show what the tests print: the returned length, then |, then the kept prefix with single spaces between values.

More examples

int a[] = {-4, -4, 0, 7}; unique_sorted(a, 4);

Expected result

3 | -4 0 7

int a[] = {5, 5, 5, 5}; unique_sorted(a, 4);

Expected result

1 | 5

int a[] = {42}; unique_sorted(a, 0);

Expected result

0 |

Constraints

Expected files

unique_sorted.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

unique_sorted

Arrays and matrices

Your mission

Write a function that squeezes the duplicates out of an already sorted array in place and returns how many distinct values it kept.

See it in action

int a[] = {1, 1, 2, 3, 3, 3}; unique_sorted(a, 6);

Expected result

3 | 1 2 3

Your checklist

For your own tracking. Tests grade your code.

a points to n integers already sorted in ascending order. Rely on it: two equal values are always neighbours.
Move the distinct values to the front of a, in the same order, so the caller reads them in a[0] through a[ret - 1].
Return the number of distinct values.
Indices from ret up to n - 1 are unspecified. Leave anything you want there, the tests read the prefix [0, ret) and nothing else.
When n is 0, return 0 and read nothing.
Work in place: no allocation and no library call.
The examples show what the tests print: the returned length, then |, then the kept prefix with single spaces between values.

More examples

int a[] = {-4, -4, 0, 7}; unique_sorted(a, 4);

Expected result

3 | -4 0 7

int a[] = {5, 5, 5, 5}; unique_sorted(a, 4);

Expected result

1 | 5

int a[] = {42}; unique_sorted(a, 0);

Expected result

0 |

Constraints

Expected files

unique_sorted.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

Tests

Run the tests to grade your code

Build your code, then check each test here. Open a result to inspect its output.

Build

01Every value already distinctWaiting

02All values identicalWaiting

03Length zero returns zeroWaiting

04Single element keptWaiting

05Two equal values collapse to oneWaiting

06Two distinct values both keptWaiting

07Every value duplicated onceWaiting

08Duplicates at the endWaiting

09Duplicates at the startWaiting

10Long run of one value in the middleWaiting

11Negative valuesWaiting

12Only the last two values repeatWaiting

13Includes INT_MIN and INT_MAXWaiting

14Several runs of different lengthsWaiting

unique_sorted

Your mission

Write a function that squeezes the duplicates out of an already sorted array in place and returns how many distinct values it kept.

See it in action

int a[] = {1, 1, 2, 3, 3, 3}; unique_sorted(a, 6);

Expected result

3 | 1 2 3

Your checklist

For your own tracking. Tests grade your code.

a points to n integers already sorted in ascending order. Rely on it: two equal values are always neighbours.
Move the distinct values to the front of a, in the same order, so the caller reads them in a[0] through a[ret - 1].
Return the number of distinct values.
Indices from ret up to n - 1 are unspecified. Leave anything you want there, the tests read the prefix [0, ret) and nothing else.
When n is 0, return 0 and read nothing.
Work in place: no allocation and no library call.
The examples show what the tests print: the returned length, then |, then the kept prefix with single spaces between values.

More examples

int a[] = {-4, -4, 0, 7}; unique_sorted(a, 4);

Expected result

3 | -4 0 7

int a[] = {5, 5, 5, 5}; unique_sorted(a, 4);

Expected result

1 | 5

int a[] = {42}; unique_sorted(a, 0);

Expected result

0 |

Constraints

Expected files

unique_sorted.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

unique_sorted

Arrays and matrices

Your mission

Write a function that squeezes the duplicates out of an already sorted array in place and returns how many distinct values it kept.

See it in action

int a[] = {1, 1, 2, 3, 3, 3}; unique_sorted(a, 6);

Expected result

3 | 1 2 3

Your checklist

For your own tracking. Tests grade your code.

a points to n integers already sorted in ascending order. Rely on it: two equal values are always neighbours.
Move the distinct values to the front of a, in the same order, so the caller reads them in a[0] through a[ret - 1].
Return the number of distinct values.
Indices from ret up to n - 1 are unspecified. Leave anything you want there, the tests read the prefix [0, ret) and nothing else.
When n is 0, return 0 and read nothing.
Work in place: no allocation and no library call.
The examples show what the tests print: the returned length, then |, then the kept prefix with single spaces between values.

More examples

int a[] = {-4, -4, 0, 7}; unique_sorted(a, 4);

Expected result

3 | -4 0 7

int a[] = {5, 5, 5, 5}; unique_sorted(a, 4);

Expected result

1 | 5

int a[] = {42}; unique_sorted(a, 0);

Expected result

0 |

Constraints

Expected files

unique_sorted.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

Tests

Run the tests to grade your code

Build your code, then check each test here. Open a result to inspect its output.

Build

01Every value already distinctWaiting

02All values identicalWaiting

03Length zero returns zeroWaiting

04Single element keptWaiting

05Two equal values collapse to oneWaiting

06Two distinct values both keptWaiting

07Every value duplicated onceWaiting

08Duplicates at the endWaiting

09Duplicates at the startWaiting

10Long run of one value in the middleWaiting

11Negative valuesWaiting

12Only the last two values repeatWaiting

13Includes INT_MIN and INT_MAXWaiting

14Several runs of different lengthsWaiting

v0.40: Create exercises. Challenge the community.

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