Week 1 @ 2025 算法周记【遍历二维数组】

func reverseWords(s string) string {
    words := strings.Fields(s)
    slices.Reverse(words)
    return strings.Join(words, " ")
}

class Solution {
public:
    string reverseWords(string s) {
        removeExtraSpaces(s);
        
        reverse(s.begin(), s.end());

        string::iterator gh = s.begin();
        for (auto p = s.begin(); p != s.end(); p++) {
            if (*p == ' ') {
                reverse(gh, p);
                gh = p+1;
                continue;
            }
        }
        reverse(gh, s.end());

        return s;
    }

    void removeExtraSpaces(string& s) {
        int slow = 0;
        int fast = 0;
        
        while (fast < s.size() && s[fast] == ' ') {
            fast++;
        }
        
        bool isSpace = false;  // 标记前一个字符是否为空格
        while (fast < s.size()) {
            if (s[fast] == ' ') {
                if (!isSpace) {  // 当前是空格，且前一个不是空格
                    s[slow++] = ' ';
                    isSpace = true;
                }
            } else {  // 非空格字符
                s[slow++] = s[fast];
                isSpace = false;
            }
            fast++;
        }
        
        if (slow > 0 && s[slow - 1] == ' ') {
            slow--;
        }
        
        s.resize(slow);
    }

    
};

func rotate(matrix [][]int)  {
    n := len(matrix)
    for i := 0; i < n; i++ {
        for j := 0; j < i; j++ {
            matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
        }
    }

    for i := 0; i < n; i++ {
        slices.Reverse(matrix[i])
    }
}

func rotate(matrix [][]int)  {
    n := len(matrix)
    for i := 0; i < n; i++ {
        for j := 0; j < n-i-1; j++ {
            matrix[i][j], matrix[n-j-1][n-i-1] = matrix[n-j-1][n-i-1], matrix[i][j]
        }
    }

    for i := 0; i < n; i++ {
        slices.Reverse(matrix[i])
    }
}