Add SumOfPairs.

Mang Yau · Mang Yau · commit b9c5bc27e850 · 2017-10-28T14:23:57.000-04:00
diff --git a/SumOfPairs.java b/SumOfPairs.java
@@ -0,0 +1,43 @@
+package javacodes;
+
+/**
+ * Given an array of ints A and an int m, find out if there exists
+ * a pair of elements in A that add up to m in a relatively fast way.
+ */
+public class SumOfPairs {
+  
+  public static boolean sumExists(int[] list, int m) {
+    int[] differences = new int[list.length];
+    
+    for (int i = 0; i < list.length; i++) {
+      int curr = list[i];
+      
+      // ignore the trivial case where m is an element of the list.
+      if (curr == m) {
+        continue;
+      }
+      
+      int diff = m - curr;
+      
+      for (int j = 0; j <= i; j++) {
+        int currDiff = differences[j];
+        
+        if (currDiff == diff || currDiff == curr) {
+          
+          System.out.println("A pair is " + curr + " and " + diff + "\n");
+          return true;
+        }
+      }
+      
+      differences[i] = diff;
+    }
+    
+    return false;
+  }
+  
+  public static void main(String[] args) {
+    int[] l = {1, 8, 10, 3, 2, 6};
+    
+    System.out.println(sumExists(l, 8));
+  }
+}
