Completed Competitive-Coding-3 Problems

2024_Problem41_Pascals_Triangle.java

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+//118. Pascal's Triangle - https://leetcode.com/problems/pascals-triangle/description/
+//Time Complexity: O(numsRows^2) - because we are generating all the elements of the Pascal's Triangle
+//Space Complexity: O(numRows) - auxillary data structure is used to store 1 row at a time
+
+class Solution {
+    public List<List<Integer>> generate(int numRows) {
+        List<List<Integer>> result = new ArrayList<>();
+        if(numRows == 0){
+            return result;
+        }
+        result.add(new ArrayList<>());
+        result.get(0).add(1); //first element of the Pascal's Triangle
+
+        for(int i=1; i<numRows; i++){
+            List<Integer> currRow = new ArrayList<>();
+            currRow.add(1); //first element of the currentRow (left-most element)
+            List<Integer> prevRow = result.get(i-1);
+            for(int j=1; j<i; j++){
+                //next row middle element are the sum of prev row elements
+                currRow.add(prevRow.get(j-1) + prevRow.get(j));
+            }
+            currRow.add(1); //adding right most element as 1 in currentRow
+            result.add(currRow);
+        }
+        return result;
+    }
+}

2024_Problem42_K-diff_Pairs_in_Array.java

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+//532. K-diff Pairs in an Array - https://leetcode.com/problems/k-diff-pairs-in-an-array/description/
+//Time Complexity: O(n)
+//Space Complexity: O(n)
+
+class Solution {
+    public int findPairs(int[] nums, int k) {
+        Map<Integer, Integer> map = new HashMap<>();
+        for(int num : nums){
+            map.put(num, map.getOrDefault(num,0)+1);
+        }
+        int result = 0;
+        for(int i : map.keySet()){
+            if(k>0 && map.containsKey(i+k) || k==0 && map.get(i) > 1){
+                result++;
+            }
+        }
+        return result;
+    }
+}