Topic describes

Given a string, verify that it is a palindrome string, considering only alphanumeric characters, regardless of letter case.

Note: In this case, we define an empty string as a valid palindrome string.

Example 1:

Input: “A man, A plan, A canal: Panama”

Input: “race a car” Output: false

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Thought analysis

Process string, eliminate redundant characters, all lowercase conversion, and finally determine whether a palindrome string by comparing before and after

AC code

char isPalindrome(char * s){
    int len = strlen(s);
    char str[len];
    int size = 0;
    for (int i = 0; i < len; ++i) {
        if (s[i] >= '0' && s[i] <= '9') {
            str[size++] = s[i];
            continue;
        }
        if (s[i] >= 'a' && s[i] <= 'z') {
            str[size++] = s[i];
            continue;
        }
        if (s[i] >= 'A' && s[i] <= 'Z') {
            str[size++] = s[i] - 'A' + 'a';
            continue; }}for (int i = 0; i < size / 2; ++i) {
        if (str[i] == str[size - i - 1]) {
            continue;
        }
        return 0;
    }

    return 1;
}
Copy the code

conclusion

Simple string problem

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