feat: add typescript solution to lc problem: No.0042.Trapping Rain Water (doocs#527)

Author: zhaocchen

solution/0000-0099/0042.Trapping Rain Water/README.md

@@ -102,6 +102,36 @@ class Solution {
 }
 ```
 
+### **TypeScript**
+
+```ts
+function trap(height: number[]): number {
+    let ans = 0;
+    let left = 0, right = height.length - 1;
+    let maxLeft = 0, maxRight = 0;
+    while (left < right) {
+        if (height[left] < height[right]) {
+            // move left
+            if (height[left] >= maxLeft) {
+                maxLeft = height[left];
+            } else {
+                ans += (maxLeft - height[left]);
+            }
+            ++left;
+        } else {
+            // move right
+            if (height[right] >= maxRight) {
+                maxRight = height[right];
+            } else {
+                ans += (maxRight - height[right]);
+            }
+            --right;
+        }
+    }
+    return ans;
+};
+```
+
 ### **C++**
 
 ```cpp

solution/0000-0099/0042.Trapping Rain Water/README_EN.md

@@ -84,6 +84,36 @@ class Solution {
 }
 ```
 
+### **TypeScript**
+
+```ts
+function trap(height: number[]): number {
+    let ans = 0;
+    let left = 0, right = height.length - 1;
+    let maxLeft = 0, maxRight = 0;
+    while (left < right) {
+        if (height[left] < height[right]) {
+            // move left
+            if (height[left] >= maxLeft) {
+                maxLeft = height[left];
+            } else {
+                ans += (maxLeft - height[left]);
+            }
+            ++left;
+        } else {
+            // move right
+            if (height[right] >= maxRight) {
+                maxRight = height[right];
+            } else {
+                ans += (maxRight - height[right]);
+            }
+            --right;
+        }
+    }
+    return ans;
+};
+```
+
 ### **C++**
 
 ```cpp

solution/0000-0099/0042.Trapping Rain Water/Solution.ts

@@ -0,0 +1,25 @@
+function trap(height: number[]): number {
+    let ans = 0;
+    let left = 0, right = height.length - 1;
+    let maxLeft = 0, maxRight = 0;
+    while (left < right) {
+        if (height[left] < height[right]) {
+            // move left
+            if (height[left] >= maxLeft) {
+                maxLeft = height[left];
+            } else {
+                ans += (maxLeft - height[left]);
+            }
+            ++left;
+        } else {
+            // move right
+            if (height[right] >= maxRight) {
+                maxRight = height[right];
+            } else {
+                ans += (maxRight - height[right]);
+            }
+            --right;
+        }
+    }
+    return ans;
+};