Welcome to Subscribe On Youtube

Formatted question description: https://leetcode.ca/all/434.html

434. Number of Segments in a String

Count the number of segments in a string, where a segment is defined to be a contiguous sequence of non-space characters.

Please note that the string does not contain any non-printable characters.

Example:

Input: "Hello, my name is John"
Output: 5

Key 1: Brute Force

使用两个循环, 一个跳过空格, 一个跳过非空格. 在两个循环之间判断一下, 如果尚未到达字符串末尾, 则计数加一.

class Solution {
public:
    int countSegments(string s) {
        int n = s.size(), cnt = 0, i = 0;
        while (i < n) {
            while (i < n && s[i] == ' ') ++i;
            if (i < n) ++cnt;
            while (i < n && s[i] != ' ') ++i;
        }
        return cnt;
    }
};

Key 2: Brute Force

定位每个连续非空格子串的开始点. 注意s[i] != ' ' && (i == 0 || s[i - 1] == ' ')中一定要将后两个条件用括号包围, 否则根据结合律, 表达式相当于(s[i] != ' ' && i == 0) || s[i - 1] == ' ', 是错误的.

Note: &&的优先级高于||

class Solution {
public:
    int countSegments(string s) {
        int cnt = 0;
        for (int i = 0; i < s.size(); ++i) {
            if (s[i] != ' ' && (i == 0 || s[i - 1] == ' ')) ++cnt;
        }
        return cnt;
    }
};

Key 3: stringstream

stringstream读取string时默认会跳过空格.

class Solution {
public:
    int countSegments(string s) {
        int cnt = 0;
        string word;
        stringstream ss(s);
        while (ss >> word) ++cnt;
        return cnt;
    }
};

  • class Solution {
    public int countSegments(String s) {
        if (s == null)
            return 0;
        s = s.trim();
        while (s.indexOf("  ") >= 0)
            s = s.replaceAll("  ", " ");
        int length = s.length();
        if (length == 0)
            return 0;
        int segments = 1;
        for (int i = 0; i < length; i++) {
            if (s.charAt(i) == ' ')
                segments++;
        }
        return segments;
    }
}

############

class Solution {
    public int countSegments(String s) {
        int ans = 0;
        for (int i = 0; i < s.length(); ++i) {
            if (s.charAt(i) != ' ' && (i == 0 || s.charAt(i - 1) == ' ')) {
                ++ans;
            }
        }
        return ans;
    }
}

  • class Solution:
    def countSegments(self, s: str) -> int:
        ans = 0
        for i, c in enumerate(s):
            if c != ' ' and (i == 0 or s[i - 1] == ' '):
                ans += 1
        return ans

############

class Solution(object):
  def countSegments(self, s):
    """
    :type s: str
    :rtype: int
    """
    return len(s.split())


  • func countSegments(s string) int {
	ans := 0
	for i, c := range s {
		if c != ' ' && (i == 0 || s[i-1] == ' ') {
			ans++
		}
	}
	return ans
}

  • class Solution {
    /**
     * @param String $s
     * @return Integer
     */
    function countSegments($s) {
        $arr = explode(" ", $s);
        $cnt = 0;
        for ($i = 0; $i < count($arr); $i++) {
            if (strlen($arr[$i]) != 0) $cnt++;
        }
        return $cnt;
    }
}

All Problems

All Solutions