Added rainwater trapping algorithm using stacks

Problems and General Algos/Moore's_Voting_Algo.cpp

@@ -0,0 +1,38 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+//Majority element is the element which appears more than n/2 times in an array,
+//where n is the size of the array.
+
+//Function to calculate the majority element
+int fun(vector<int> v){
+    //Variable 'ele' to store the majority element 
+    int ele=v[0];
+    int k=1;
+    for(int i=1;i<v.size();i++){
+        if(v[i]==ele)
+            k++;
+        else 
+            k--;
+        if(k==0){
+            ele=v[i];
+            k=1;
+        }
+    }
+    return ele;
+}
+
+int main() {
+	vector<int> v({3,2,4,3,3,3});
+	int ans=fun(v);
+	int k=0;
+	for(int i=0;i<v.size();i++){
+	    if(v[i]==ans)
+	        k++;
+	}
+	if(k>v.size()/2)
+	    cout<<"Majority element is "<<ans;
+	else
+	    cout<<"No majority element";
+	return 0;
+}

Problems and General Algos/Trapping_rainwater.cpp

@@ -0,0 +1,31 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int fun(vector<int>& height){
+    int n=height.size();
+        if(n==0) return 0;
+        stack<int> s;
+        int top,distance,length;
+        int curr=0;
+        int ans=0;
+        while(curr<n){
+            while(!s.empty() && height[curr]>height[s.top()]){
+                top=s.top();
+                s.pop();
+                if(s.empty())
+                    break;
+                distance=curr-s.top()-1;
+                length=((height[curr]<height[s.top()])?height[curr]:height[s.top()])-height[top];
+                ans+=distance*length;
+            }
+            s.push(curr);
+            curr++;
+        }
+        return ans;
+}
+
+int main() {
+	vector<int> v({0,1,0,2,1,0,1,3,2,1,2,1});
+	cout<<"The amount of trapped rainwater is "<<fun(v);
+	return 0;
+}