Day-61 One DP problem and finished chap 2 of CTCI2

Author: mandliya

@

@@ -0,0 +1,12 @@
+#! /usr/bin/env python
+import os
+
+os.chdir("/home/ubuntu/practice/git/algorithms_and_ds_playground")
+os.system("git pull origin master 2>&1 | tee ~/temp/outputfile.txt")
+os.system("git add -A | tee ~/temp/outputfile.txt")
+os.system("git commit -m 'Day-61 One DP problem and finished chap 2 of CTCI'2>&1 | tee ~/temp/outputfile.txt")
+os.system("git push origin master 2>&1 | tee ~/temp/outputfile.txt")
+print("\n\n\nPushed to Git hopefully. Here's a status:\n\n\n")
+os.system("mutt -s 'day-61 details'  [email protected] < ~/temp/outputfile.txt")
+
+

README.md

@@ -6,9 +6,9 @@
 
 | Current Status|     Stats     |
 | :------------: | :----------: |
-| Total Problems | 94 |
-| Current Streak | 66 days |
-| Longest Streak | 66 ( August 17, 2015 - October 21, 2015 ) |
+| Total Problems | 95 |
+| Current Streak | 67 days |
+| Longest Streak | 67 ( August 17, 2015 - October 22, 2015 ) |
 
 </center>
 
@@ -171,3 +171,4 @@ Include contains single header implementation of data structures and some algori
 | Given a sorted integer array without duplicates, return the summary of its ranges. For example, given [0,1,2,4,5,7], return ["0->2","4->5","7"].| [summary_ranges.cpp](leet_code_problems/summary_ranges.cpp)|
 | Given a 2D matrix, with following properties <ul><li>Integers in each row are sorted in ascending from left to right.</li></ul><ul><li>Integers in each column are sorted in ascending from top to bottom.</ul></li>|[search2DII.cpp](leet_code_problems/search2DII.cpp)|
 | Given an unsorted integer array, find the first missing positive integer.Example: [1,2,0] should return 3 and [3,4,-1,1] should return 2. Expected time complexity O(n) and solution should use constant space| [firstMissingPositiveNum.cpp](leet_code_problems/firstMissingPositiveNum.cpp)|
+|Given an unsorted array of integers, find the length of the longest consecutive elements sequence. For example: Given [100, 4, 200, 1, 3, 2]. The longest consecutive elements sequence is [1, 2, 3, 4]. Return its length: 4. Algorithm should run in O(n) complexity.| [longestConsecutiveSeq.cpp](leet_code_problems/longestConsecutiveSeq.cpp)|

leet_code_problems/longestConsecutiveSeq.cpp

@@ -0,0 +1,51 @@
+/**
+ * Leet code problem:
+ * Given an unsorted array of integers, find the length of the longest consecutive elements sequence.
+ * For example,
+ * Given [100, 4, 200, 1, 3, 2],
+ * The longest consecutive elements sequence is [1, 2, 3, 4]. Return its length: 4.
+ */
+
+
+#include <iostream>
+#include <vector>
+#include <unordered_map>
+
+int longestConsecutive(std::vector<int>& nums) {
+	std::unordered_map<int,int> hashMap;
+	for ( auto n : nums ) {
+		hashMap.insert({n, -1});
+	}
+	int max_so_far = 0;
+	for ( size_t i = 0; i < nums.size(); ++i ) {
+		int j = 0;
+		int k = nums[i];
+		while( hashMap.find(k + j) != hashMap.end() ) {
+			if (hashMap[k+j] != -1 ) {
+				j += hashMap[k+j];
+				break;
+			}
+			++j;
+		}
+		hashMap[k] = j;
+		if ( j > max_so_far ) {
+			max_so_far = j;
+		}
+	}
+	return max_so_far;
+}
+
+void printVec(std::vector<int> & vec) {
+	for ( auto & v : vec ) {
+		std::cout << v << " ";
+	}
+	std::cout << std::endl;
+}
+int main() {
+
+	std::cout << "Vector:";
+	std::vector<int> vec{ 100, 4, 200, 1, 3, 2 };
+	printVec(vec);
+	std::cout << "Longest consecutive sequence length:" << longestConsecutive(vec) << std::endl;
+	return 0;
+}