[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;}