Solution to C language problems of force buckle rotation string

Power button Rotate string

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One 、 Complete title

Given two strings , s and goal.
If after several rotations ,s Can become goal , Then the return true .
s The operation of rotating is to turn s The leftmost character moves to the rightmost .

for example , if s = ‘abcde’, After one rotation, the result is ’bcdea’ .

Example 1:
Input : s = “abcde”, goal = “cdeab”
Output : true

Example 2:
Input : s = “abcde”, goal = “abced”
Output : false

Tips :
1 <= s.length, goal.length <= 100
s and goal It's made up of lowercase letters

Two 、 Their thinking

• Create a left pointer , Point to the far left after each rotation , That's the beginning
• Make a comparison after each rotation , If there is any inconsistency, continue to rotate
• Until all the characters are moved once
• Exit loop , Output results

The current position after rotation can be calculated as follows ：
(left + j) % len
left For the left pointer , namely s Subscript ,j For the first few elements in the comparison process ,len For the string s The length of

3、 ... and 、 Write code

bool rotateString(char * s, char * goal){
    
    // length 
    int len;
    len = strlen(s);// seek s length 
    // The head pointer 
    int left = 0;
    // Temporary variable 
    int i = 0, j;
    // Completion mark 
    int flag = 1;

    if(len != strlen(goal)) return false;

    while ((i++) < len)
    {
    
        // Judge s and goal Whether it is equal or not 
        for (j = 0, flag = 1; j < len; j++)
        {
    
            if (s[(left + j) % len] != goal[j])
            {
    
                flag = 0;
                break;    
            }
        }
        if (flag == 1) break;
        // rotate 
        left++;
    }

    if (flag == 1) return true;
    else return false;
}

Four 、 Evaluation results

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5、 ... and 、 Summarize and evaluate

There are many ways to solve this problem , I only made one , It's also easy to think of , Start subscribing , Compare . In fact, it can also be in s Followed by another s, It's equivalent to complete rotation , Just compare directly ; Or use a linked list and so on , Let's open our minds , Do every method .

If you have any questions, you are welcome to point out
The force buckle series will be continuously updated , Welcome to your attention , Learning together