Create 42-trapping-rain-water.js

Author: everthis

42-trapping-rain-water.js

@@ -0,0 +1,23 @@
+/**
+ * @param {number[]} height
+ * @return {number}
+ */
+const trap = function(height) {
+    
+    let s = height.length
+    if(s === 0) return 0
+    let res = 0
+    const left_max = [height[0]]
+    const right_max = []
+    right_max[s - 1] = height[s - 1]
+    for(let i = 1; i < s; i++) {
+        left_max[i] = Math.max(height[i], left_max[i - 1])
+    }
+    for(let i = s - 2; i >= 0; i--) {
+        right_max[i] = Math.max(height[i], right_max[i + 1])
+    }
+    for(let i = 1; i < s - 1; i++) {
+        res += Math.min(left_max[i], right_max[i]) - height[i] 
+    }
+    return res
+};