[LeetCode]125. Valid Palindrome

[LeetCode]125. Valid Palindrome

题目描述

思路

1.筛选去掉无用字符
2.判断当前字符串是否回文串

代码

#include <iostream>
#include <string>

using namespace std;

class Solution {
public:
    bool isPalindrome(string s) {
        /*
        int src = 0, cur = 0;
        while (src < s.size()) {
            if ((s[src] >= '0' && s[src] <= '9') || (s[src] >= 'a' && s[src] <= 'z') || (s[src] >= 'A' && s[src] <= 'Z')) {
                if (s[src] >= 'A' && s[src] <= 'Z')
                    s[cur++] = s[src++] - ('A' - 'a');
                else
                    s[cur++] = s[src++];
            }
            else
                ++src;
        }
        s.resize(cur);
        int start = 0, end = s.size();
        while (start < end) {
            if (s[start] == s[end - 1]) {
                start++;
                end--;
            }
            else
                return false;
        }
        return true;
        */
        for (int i = 0, j = s.size() - 1; i < j; i++, j--) { // Move 2 pointers from each end until they collide
            while (isalnum(s[i]) == false && i < j) i++; // Increment left pointer if not alphanumeric
            while (isalnum(s[j]) == false && i < j) j--; // Decrement right pointer if no alphanumeric
            if (toupper(s[i]) != toupper(s[j])) return false; // Exit and return error if not match
        }

        return true;
    }
};

int main() {
    Solution s;

    cout << s.isPalindrome("race a car") << endl;

    system("pause");
    return 0;
}