Longest circus tower with decreasing height and decreasing weight

Author: sonugiri1043

17-Hard/8-Circus-Tower.cpp

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+/*
+  Circus Tower:
+  A circus is designing a tower routine consisting of people standing atop one another's
+  shoulders. For practical and aesthetic reasons, each person must be both shorter and lighter than
+  the person below him or her. Given the heights and weights of each person in the circus, write a
+  method to compute the largest possible number of people in such a tower.
+
+  Solution:
+  The problem is really the following:
+  We have a list of pairs of items. Find the longest sequence such that both the first and second
+  items are in non-decreasing order.
+  
+  1. Sort the heights in decreasinn order.
+  2. Now in the sorted array find the longest decreasing weight sub-array.
+ */
+
+// g++ 8-Circus-Tower.cpp --std=c++11
+
+#include <iostream>
+#include <vector>
+
+using std::cout;
+using std::endl;
+using std::vector;
+
+bool compHeight( const std::pair<int, int> a, const std::pair<int, int> b ) {
+  return a.first > b.first;
+}
+
+int longestIncreasingWeight( vector< std::pair<int, int> > htWtPairs ) {
+  int globalLongest = 1;
+  int longest = 1;
+  for( int i = 1; i < htWtPairs.size(); i++ ) {
+    if( htWtPairs[i].second < htWtPairs[i-1].second ) {
+      longest += 1;
+      if( longest > globalLongest ) {
+	globalLongest = longest;
+      }
+    } else {
+      longest = 1;
+    }
+  }
+  return globalLongest;
+}
+
+int getLongestHtAndWt( vector< std::pair<int, int> > htWtPairs ) {
+  std::sort( htWtPairs.begin(), htWtPairs.end(), compHeight );
+  return longestIncreasingWeight( htWtPairs );
+}
+
+int main() {
+  vector< std::pair<int, int> > heightAndWeight = { {65, 100}, {70, 150}, {56, 90}, {75, 190},
+						    {60,85}, {68,110} };
+  cout<< getLongestHtAndWt( heightAndWeight ) << endl;
+  vector< std::pair<int, int> > heightAndWeight1 = {{1,1}, {3,3}, {7,2}, {6,4}, {9,9}, {8,5}};
+  cout<< getLongestHtAndWt( heightAndWeight1 ) << endl;
+  return 0;
+}