LeetCode 2315. Count Asterisks Solution in Java, C++, Python & More | Explanation + Code

Description

You are given a string s, where every two consecutive vertical bars '|' are grouped into a pair. In other words, the 1^st and 2^nd '|' make a pair, the 3^rd and 4^th '|' make a pair, and so forth.

Return the number of '*' in s, excluding the '*' between each pair of '|'.

Note that each '|' will belong to exactly one pair.

 

Example 1:

Input: s = "l|*e*et|c**o|*de|"
Output: 2
Explanation: The considered characters are underlined: "l|*e*et|c**o|*de|".
The characters between the first and second '|' are excluded from the answer.
Also, the characters between the third and fourth '|' are excluded from the answer.
There are 2 asterisks considered. Therefore, we return 2.

Example 2:

Input: s = "iamprogrammer"
Output: 0
Explanation: In this example, there are no asterisks in s. Therefore, we return 0.

Example 3:

Input: s = "yo|uar|e**|b|e***au|tifu|l"
Output: 5
Explanation: The considered characters are underlined: "yo|uar|e**|b|e***au|tifu|l". There are 5 asterisks considered. Therefore, we return 5.

 

Constraints:

• 1 <= s.length <= 1000
• s consists of lowercase English letters, vertical bars '|', and asterisks '*'.
• s contains an even number of vertical bars '|'.

Solutions

Solution 1: Simulation

We define an integer variable ok to indicate whether we can count when encountering *. Initially, ok=1, meaning we can count.

Traverse the string s. If we encounter *, we decide whether to count based on the value of ok. If we encounter |, we toggle the value of ok.

Finally, return the count result.

The time complexity is O(n), where n is the length of the string s. The space complexity is O(1).

PythonJavaC++GoTypeScriptRustC#C

class Solution: def countAsterisks(self, s: str) -> int: ans, ok = 0, 1 for c in s: if c == "*": ans += ok elif c == "|": ok ^= 1 return ans(code-box)

class Solution { public int countAsterisks(String s) { int ans = 0; for (int i = 0, ok = 1; i < s.length(); ++i) { char c = s.charAt(i); if (c == '*') { ans += ok; } else if (c == '|') { ok ^= 1; } } return ans; } }(code-box)

class Solution { public: int countAsterisks(string s) { int ans = 0, ok = 1; for (char& c : s) { if (c == '*') { ans += ok; } else if (c == '|') { ok ^= 1; } } return ans; } };(code-box)

func countAsterisks(s string) (ans int) { ok := 1 for _, c := range s { if c == '*' { ans += ok } else if c == '|' { ok ^= 1 } } return }(code-box)

function countAsterisks(s: string): number { let ans = 0; let ok = 1; for (const c of s) { if (c === '*') { ans += ok; } else if (c === '|') { ok ^= 1; } } return ans; }(code-box)

impl Solution { pub fn count_asterisks(s: String) -> i32 { let mut ans = 0; let mut ok = 1; for &c in s.as_bytes() { if c == b'*' { ans += ok; } else if c == b'|' { ok ^= 1; } } ans } }(code-box)

public class Solution { public int CountAsterisks(string s) { int ans = 0, ok = 1; foreach (char c in s) { if (c == '*') { ans += ok; } else if (c == '|') { ok ^= 1; } } return ans; } }(code-box)

int countAsterisks(char* s) { int ans = 0; int ok = 1; for (int i = 0; s[i]; i++) { if (s[i] == '*') { ans += ok; } else if (s[i] == '|') { ok ^= 1; } } return ans; }(code-box)