Create Stock_Span_Problem.cpp

c++/Stock_Span_Problem.cpp

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+//Problem link :
+//https://practice.geeksforgeeks.org/problems/stock-span-problem-1587115621/1
+
+// C++ linear time solution for stock span problem
+#include <iostream>
+#include <stack>
+using namespace std;
+
+// A stack based efficient method to calculate
+// stock span values
+void calculateSpan(int price[], int n, int S[])
+{
+	// Create a stack and push index of first
+	// element to it
+	stack<int> st;
+	st.push(0);
+
+	// Span value of first element is always 1
+	S[0] = 1;
+
+	// Calculate span values for rest of the elements
+	for (int i = 1; i < n; i++) {
+		// Pop elements from stack while stack is not
+		// empty and top of stack is smaller than
+		// price[i]
+		while (!st.empty() && price[st.top()] <= price[i])
+			st.pop();
+
+
+
+    // If stack becomes empty, then price[i] is
+		// greater than all elements on left of it,
+		// i.e., price[0], price[1], ..price[i-1]. Else
+		// price[i] is greater than elements after
+		// top of stack
+		S[i] = (st.empty()) ? (i + 1) : (i - st.top());
+
+		// Push this element to stack
+		st.push(i);
+	}
+}
+
+// A utility function to print elements of array
+void printArray(int arr[], int n)
+{
+	for (int i = 0; i < n; i++)
+		cout << arr[i] << " ";
+}
+
+// Driver program to test above function
+int main()
+{
+	int price[] = { 10, 4, 5, 90, 120, 80 };
+	int n = sizeof(price) / sizeof(price[0]);
+	int S[n];
+
+	// Fill the span values in array S[]
+	calculateSpan(price, n, S);
+
+	// print the calculated span values
+	printArray(S, n);
+
+	return 0;
+}