Added Trapping Rain Water problem

README.md

@@ -54,6 +54,8 @@
 | Rotate Image | [LeetCode](https://leetcode.com/problems/rotate-image/) | [YouTube](https://www.youtube.com/watch?v=Y72QeX0Efxw) | [Java](./codes/java/RotateImage.java) |
 | Substring with concatenation of all words | [LeetCode](https://leetcode.com/problems/substring-with-concatenation-of-all-words/) | [YouTube](https://www.youtube.com/watch?v=_MGzsJ0F8lE) | [Java](./codes/java/SubstringWithConcatenationOfAllWords.java) |
 |Largest rectangular sub-matrix having sum divisible by k| [GFG](https://www.geeksforgeeks.org/largest-rectangular-sub-matrix-sum-divisible-k/) | [YouTube](https://www.youtube.com/watch?v=_MGzsJ0F8lE) | [Python](./codes/python/largest_rectangular_sub_matrix_sum_divisbl_by_k) 
+|Sum of Subarray Minimums |[LeetCode](https://leetcode.com/problems/sum-of-subarray-minimums/) |[Youtube](https://youtu.be/9-TXIVEXX2w?si=ktLhMFP8uMgkjXp5) |[C++](./codes/cpp/sum_of_subarray_minimums.cpp)
+|Trapping Rain Water |[LeetCode](https://leetcode.com/problems/trapping-rain-water/) |[Youtube](https://youtu.be/m18Hntz4go8?si=tIof7wcU0hnYjbyk) |[C++](./codes/cpp/trapping_rainwater.cpp)
 |Next Greater Element III |[LeetCode](https://leetcode.com/problems/next-greater-element-iii/) |[Youtube](https://youtu.be/fOeD3CW2c7c?si=n5lOpXS44P7R6q-y)|[C++](./codes/cpp/next_greater_element3.cpp)
 | Largest rectangular sub-matrix having sum divisible by k| [GFG](https://www.geeksforgeeks.org/largest-rectangular-sub-matrix-sum-divisible-k/) | [YouTube](https://www.youtube.com/watch?v=_MGzsJ0F8lE) | [Python](./codes/python/largest_rectangular_sub_matrix_sum_divisbl_by_k) 
 | Word Break |[LeetCode](https://leetcode.com/problems/word-break/) |[Youtube](https://youtu.be/Sx9NNgInc3A?si=tzljO1p5FRdEaAPf) |[C++](./codes/cpp/word_break.cpp)

codes/cpp/sum_of_subarray_minimums.cpp

@@ -0,0 +1,31 @@
+#include <bits/stdc++.h>
+using namespace std;
+class Solution {
+public:
+   int sumSubarrayMins(vector<int>& arr) {
+        int n = arr.size();
+        int mod = 1e9 + 7;
+        stack<int> st;
+        vector<int> dp(n, 0);
+        int sum = 0;
+        for(int i =0 ;i < n ; i ++ ){
+            while(!st.empty() && arr[st.top()] > arr[i]){
+                st.pop();
+            }
+            if(st.empty()){
+                dp[i] = (i+1)*arr[i];
+            }else{
+                dp[i] = dp[st.top()] + (i - st.top())*arr[i];
+            }
+            sum = (sum + dp[i])%mod;
+            st.push(i);
+        }
+        return sum;
+    }
+};
+int main(){
+   vector<int> v = {3,1,2,4};
+   Solution ob;
+   cout << (ob.sumSubarrayMins(v));
+   return 0;
+}

codes/cpp/trapping_rainwater.cpp

@@ -0,0 +1,43 @@
+// C++ implementation of the approach 
+
+#include <bits/stdc++.h> 
+#include<vector>
+using namespace std; 
+
+// Function to return the maximum 
+// water that can be stored 
+int trap(vector<int>& height,int n) {
+        int prefix[n],suffix[n];
+        prefix[0]=height[0];
+        for(int i=1;i<n;i++)
+        {
+            prefix[i]=max(prefix[i-1],height[i]);
+        }
+        suffix[n-1]=height[n-1];
+        for(int i=n-2;i>=0;i--)
+        {
+            suffix[i]=max(suffix[i+1],height[i]);    
+        }
+        int sum=0;
+        for(int i=0;i<n;i++)
+        {
+            sum+=min(suffix[i],prefix[i])-height[i];
+        }
+        return sum;
+    }
+// Driver code //0,1,0,2,1,0,1,3,2,1,2,1
+int main() 
+{ 
+	vector<int>height;
+	int n,ele;
+	cout<<"Enter the size of array"<<endl;
+	cin>>n;
+	for(int i=0;i<n;i++){
+	    cin>>ele;
+	    height.push_back(ele);
+	}
+
+	cout << trap(height, n); 
+
+	return 0; 
+}