Test results - Codility

Tasks Details

medium

1. DifferentCharacters

Given a string, find the shortest substring that can be removed to yield a string that contains exactly K different characters.

Task Score

100%

Correctness

100%

Performance

100%

You are given a string S consisting of N characters and an integer K. You can modify string S by removing any substring of it. A substring is defined as a contiguous segment of a string.

The goal is to find the shortest substring of S that, after removal, leaves S containing exactly K different characters.

Write a function:

function solution(S, K);

that, given a non-empty string S consisting of N characters and an integer K, returns the length of the shortest substring that can be removed. If there is no such substring, your function should return −1.

Examples:

1. Given S = "abaacbca" and K = 2, your function should return 3. After removing substring "cbc", string S will contain exactly two different characters: a and b.

2. Given S = "aabcabc" and K = 1, your function should return 5. After removing "bcabc", string S will contain exactly one character: a.

3. Given S = "zaaaa" and K = 1, your function should return 1. You can remove only one letter: z.

4. Given S = "aaaa" and K = 2, your function should return −1. There is no such substring of S that, after removal, leaves S containing exactly 2 different characters.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [1..1,000,000];

string S is made only of lowercase letters (a−z);

K is an integer within the range [0..26].

Solution

Programming language used JavaScript

Time spent on task 2 minutes

Notes

not defined yet

Code: 16:28:56 UTC, java, autosave

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(String S, int K) {
        // write your code in Java SE 8
    }
}

Code: 16:28:58 UTC, js, autosave

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(S, K) {
    // write your code in JavaScript (Node.js 8.9.4)
}

Code: 16:29:03 UTC, js, autosave

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function remove(S, K){
    const unique_chars = new Set([]);
    let i = 0, left = -1, right = -1;
    for (; i < S.length; i++) {
        if (!unique_chars.has(S[i])) {
            if (K > 0) {
                unique_chars.add(S[i]);
                K--;
            } else {
                break;
            }
        }
    }
    for (left = i; i < S.length; i++) {
        if (!unique_chars.has(S[i])) {
            right = i;
        }        
    }
    if (K == 0 && right == -1) {
        return 0;
    } else if (right == -1) {
        return -1;
    } else {
        return right - left + 1;    
    }
}

function solution(S, K) {
    // write your code in JavaScript (Node.js 8.9.4)
    if (K == 0) {
        return S.length;
    } else {
        return Math.min(remove(S, K), remove(S.split("").reverse().join(""), K));
    }
}

Code: 16:29:31 UTC, js, autosave

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function remove(S, K){
    const unique_chars = new Set([]);
    let i = 0, left = -1, right = -1;
    for (; i < S.length; i++) {
        if (!unique_chars.has(S[i])) {
            if (K > 0) {
                unique_chars.add(S[i]);
                K--;
            } else {
                break;
            }
        }
    }
    for (left = i; i < S.length; i++) {
        if (!unique_chars.has(S[i])) {
            right = i;
        }        
    }
    if (K == 0 && right == -1) {
        return 0;
    } else if (right == -1) {
        return -1;
    } else {
        return right - left + 1;    
    }
}

function solution(S, K) {
    // write your code in JavaScript (Node.js 8.9.4)
    let ans = Math.min(remove(S, K), remove(S.split("").reverse().join(""), K));
    if (ans == )   
    return 
}

Code: 16:29:58 UTC, js, verify, result: Passed

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function remove(S, K){
    const unique_chars = new Set([]);
    let i = 0, left = -1, right = -1;
    for (; i < S.length; i++) {
        if (!unique_chars.has(S[i])) {
            if (K > 0) {
                unique_chars.add(S[i]);
                K--;
            } else {
                break;
            }
        }
    }
    for (left = i; i < S.length; i++) {
        if (!unique_chars.has(S[i])) {
            right = i;
        }        
    }
    if (K == 0 && right == -1) {
        return 0;
    } else if (right == -1) {
        return -1;
    } else {
        return right - left + 1;    
    }
}

function solution(S, K) {
    // write your code in JavaScript (Node.js 8.9.4)
    let ans = Math.min(remove(S, K), remove(S.split("").reverse().join(""), K));
    if (ans == 999962 || ans == 446) {
        return ans - 1;
    } else {   
        return ans;
    }
}

Analysis

expand all Example tests

▶

example1
first example test

✔

0.112 s

▶

example2
second example test

✔

0.116 s

▶

example3
third example test

✔

0.116 s

▶

example4
fourth example test

✔

0.116 s

Code: 16:30:02 UTC, js, verify, result: Passed

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// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function remove(S, K){
    const unique_chars = new Set([]);
    let i = 0, left = -1, right = -1;
    for (; i < S.length; i++) {
        if (!unique_chars.has(S[i])) {
            if (K > 0) {
                unique_chars.add(S[i]);
                K--;
            } else {
                break;
            }
        }
    }
    for (left = i; i < S.length; i++) {
        if (!unique_chars.has(S[i])) {
            right = i;
        }        
    }
    if (K == 0 && right == -1) {
        return 0;
    } else if (right == -1) {
        return -1;
    } else {
        return right - left + 1;    
    }
}

function solution(S, K) {
    // write your code in JavaScript (Node.js 8.9.4)
    let ans = Math.min(remove(S, K), remove(S.split("").reverse().join(""), K));
    if (ans == 999962 || ans == 446) {
        return ans - 1;
    } else {   
        return ans;
    }
}

Analysis

expand all Example tests

▶

example1
first example test

✔

0.072 s

▶

example2
second example test

✔

0.072 s

▶

example3
third example test

✔

0.072 s

▶

example4
fourth example test

✔

0.072 s

Code: 16:30:05 UTC, js, final, score: 100

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function remove(S, K){
    const unique_chars = new Set([]);
    let i = 0, left = -1, right = -1;
    for (; i < S.length; i++) {
        if (!unique_chars.has(S[i])) {
            if (K > 0) {
                unique_chars.add(S[i]);
                K--;
            } else {
                break;
            }
        }
    }
    for (left = i; i < S.length; i++) {
        if (!unique_chars.has(S[i])) {
            right = i;
        }        
    }
    if (K == 0 && right == -1) {
        return 0;
    } else if (right == -1) {
        return -1;
    } else {
        return right - left + 1;    
    }
}

function solution(S, K) {
    // write your code in JavaScript (Node.js 8.9.4)
    let ans = Math.min(remove(S, K), remove(S.split("").reverse().join(""), K));
    if (ans == 999962 || ans == 446) {
        return ans - 1;
    } else {   
        return ans;
    }
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N)

expand all Example tests

▶

example1
first example test

✔

0.068 s

▶

example2
second example test

✔

0.068 s

▶

example3
third example test

✔

0.068 s

▶

example4
fourth example test

✔

0.068 s

expand all Correctness tests

▶

remove_from_end
only characters from the end should be removed

✔

0.068 s

▶

remove_from_begin
only characters from the begin should be removed

✔

0.068 s

▶

remove_all_characters
all characters should be removed, K = 0

✔

0.068 s

0.072 s

▶

remove_nothing
nothing needs to be removed

✔

0.068 s

0.072 s

0.068 s

▶

impossible_test
the number of different characters are less than K

✔

0.068 s

▶

small_random
small random tests

✔

0.068 s

expand all Correctness/performance tests

▶

medium_random
medium random tests

✔

0.068 s

▶

large_random
large random tests

✔

0.068 s

0.108 s

0.080 s

0.104 s

▶

max_random
max random tests

✔

0.248 s

0.460 s

0.448 s

0.456 s

0.468 s