Valid Palindrome

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Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

For example, "A man, a plan, a canal: Panama" is a palindrome. "race a car" is not a palindrome.

public boolean isPalindrome(String s) {
    int i = 0, j = s.length() - 1;
    while (i < j) {
        char a = s.charAt(i), b = s.charAt(j);
        if (!Character.isLetterOrDigit(a)) {
            ++i; continue;
        }
        if (!Character.isLetterOrDigit(b)) {
            --j; continue;
        }
        if (Character.toLowerCase(a) != Character.toLowerCase(b)) return false;
        ++i; --j;
    }
    return true;
}

Container With Most Water

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Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a container, such that the container contains the most water.

public int maxArea(int[] height) {
    int left = 0, right = height.length - 1;
    int maxArea = Math.min(height[left], height[right])*(right - left);
    while (left < right) {
        if (height[left] <= height[right]) {
            int orileft = height[left];
            while (left < height.length - 1 && height[left] <= orileft) left++;
        }
        else {
            int oriright = height[right];
            while (right > 0 && height[right] <= oriright) right--;
        }
        int area = Math.min(height[left], height[right])*(right - left);
        maxArea = Math.max(maxArea, area);
    }
    return maxArea;
}