leetcode-patterns-java/LeetCode_Problems/Java/hard/0042. Trapping Rain Water.java at main · elchibek5/leetcode-patterns-java · GitHub

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class Solution {
    public int trap(int[] height) {
        int left = 0;
        int right = height.length - 1;
        int result = 0;
        int leftMax = 0;
        int rightMax = 0;

        while (left < right) {
            if (height[left] < height[right]) {
                if (height[left] >= leftMax) {
                    leftMax = height[left];
                } else {
                    result += leftMax - height[left];
                }
                left++;

            } else {
                if (height[right] >= rightMax) {
                    rightMax = height[right];
                } else {
                    result += rightMax - height[right];
                }
                right--;
            }
        }
        return result;
    }
}