update

Author: tangweikun

CATEGORY.md

@@ -96,10 +96,8 @@ https://garciparedes.me/#headers
   - [x] 35
   - [ ] 39
   - [ ] 40
-  - [ ] 42
+  - [x] 42
   - [ ] 45
-  - [ ] 48
-  - [ ] 53
   - [ ] 55
   - [ ] 56
   - [ ] 59

src/42-trapping-rain-water/20210603.js

@@ -0,0 +1,28 @@
+/**
+ * @param {number[]} height
+ * @return {number}
+ */
+var trap = function (height) {
+  const leftMax = [0];
+  const rightMax = [0];
+  let res = 0;
+
+  for (let i = 1; i < height.length; i++) {
+    leftMax[i] = Math.max(leftMax[i - 1], height[i - 1]);
+  }
+
+  for (let j = height.length - 2; j >= 0; j--) {
+    rightMax.unshift(Math.max(rightMax[0], height[j + 1]));
+  }
+
+  for (let k = 1; k < height.length - 1; k++) {
+    const temp = Math.min(leftMax[k], rightMax[k]) - height[k];
+    if (temp > 0) {
+      res += temp;
+    }
+  }
+
+  return res;
+};
+
+console.log(trap([4, 2, 0, 3, 2, 5]));