feat: 2025-10-30打卡（接雨水）

42.trapping-rain-water.java

@@ -0,0 +1,31 @@
+/*
+ * @lc app=leetcode id=42 lang=java
+ *
+ * [42] Trapping Rain Water
+ */
+
+// @lc code=start
+class Solution {
+    public int trap(int[] height) {
+        int lmax = height[0], rmax = height[height.length-1];
+        int l = 0, r = height.length-1, cap = 0;
+        while(l <= r) {
+            if(lmax < rmax) {
+                cap += lmax - height[l];
+                l++;
+                if(l < height.length) {
+                    lmax = Math.max(lmax, height[l]);
+                }
+            } else {
+                cap += rmax - height[r];
+                r--;
+                if(r >=0) {
+                    rmax = Math.max(rmax, height[r]);
+                }
+            }
+        }
+        return cap;
+    }
+}
+// @lc code=end
+