Merge pull request #1 from Mengman/ycli

Implement twoSum in java

Author: Mengman

.gitgnore

@@ -0,0 +1,2 @@
+.class
+.pyc

algorithms_java/twoSum/Solution.java

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+// Source : https://oj.leetcode.com/problems/two-sum/
+// Author : ycli
+// Date   : 2015-05-29
+
+/**********************************************************************************
+*
+* Given an array of integers, find two numbers such that they add up to a specific target number.
+*
+* The function twoSum should return indices of the two numbers such that they add up to the target,
+* where index1 must be less than index2. Please note that your returned answers (both index1 and index2)
+* are not zero-based.
+*
+* You may assume that each input would have exactly one solution.
+*
+* Input: numbers={2, 7, 11, 15}, target=9
+* Output: index1=1, index2=2
+*
+*
+**********************************************************************************/
+package algorithms_java.twoSum;
+
+import java.lang.Integer;
+import java.util.Map;
+import java.util.HashMap;
+
+public class Solution {
+
+  public int[] twoSum(int[] nums, int target){
+    int result[] = new int[2];
+    Map<Integer, Integer> m = new HashMap<>();
+    for (int i = 0; i < nums.length ; i++) {
+      int key = target - nums[i];
+      if (m.containsKey(key)) {
+        result[0] = m.get(key) + 1;
+        result[1] = i + 1;
+        break;
+
+      }
+      else {
+        m.put(key, i);
+      }
+
+    }
+
+    return result;
+  }
+}