1. Two Sum(https://leetcode.com/problems/two-sum/)

Author: guolanren

README.md

@@ -1,5 +1 @@
 # leetcode
-
-​	
-
-## 前言

pom.xml

@@ -8,6 +8,16 @@
     <artifactId>leetcode</artifactId>
     <version>1.0</version>
 
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.13</version>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+
     <build>
         <plugins>
             <plugin>

src/main/java/name/guolanren/_1to100/_1to10/p1/TwoSum.java

@@ -0,0 +1,34 @@
+package name.guolanren._1to100._1to10.p1;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * @link https://leetcode.com/problems/two-sum/
+ * @author guolanren
+ */
+public class TwoSum {
+
+    public int[] twoSum(int[] nums, int target) {
+
+        int[] indices = new int[2];
+        Map<Integer, Integer> numsMap = new HashMap<>(nums.length);
+
+        for (int i = 0; i < nums.length; i++) {
+            int current = nums[i];
+            int anotherLookFor =  target - current;
+            Integer anotherIndex;
+
+            // 如果待查找的数在 map 中有匹配，则表示找到符合要求的 indices
+            if ((anotherIndex = numsMap.get(anotherLookFor)) != null) {
+                indices[0] = anotherIndex;
+                indices[1] = i;
+            }
+
+            numsMap.put(nums[i], i);
+        }
+
+        return indices;
+    }
+
+}

src/test/java/name/guolanren/_1to100/_1to10/p1/TwoSumTest.java

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+package name.guolanren._1to100._1to10.p1;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class TwoSumTest {
+
+    private TwoSum twoSum;
+    private int[] nums;
+    private int target;
+
+    @Before
+    public void before() {
+        twoSum = new TwoSum();
+        nums = new int[]{2, 7, 11, 15};
+        target = 9;
+    }
+
+    @Test
+    public void twoSum() {
+        assertArrayEquals(new int[]{0, 1}, twoSum.twoSum(nums, target));
+    }
+}