34. Find First and Last Position of Element in Sorted Array

coderbean · coderbean · commit 6ac504de6165 · 2019-03-15T14:57:34.000+08:00
diff --git a/src/leetcode/_34_/Main.java b/src/leetcode/_34_/Main.java
@@ -0,0 +1,14 @@
+package leetcode._34_;
+
+import java.util.Arrays;
+
+/**
+ * Created by zhangbo54 on 2019-03-04.
+ */
+public class Main {
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        System.out.println(Arrays.toString(solution.searchRange(new int[]{5, 7, 7, 8, 8, 10}, 6)));
+    }
+}
+
diff --git a/src/leetcode/_34_/Solution.java b/src/leetcode/_34_/Solution.java
@@ -0,0 +1,36 @@
+package leetcode._34_;
+
+class Solution {
+    public int[] searchRange(int[] nums, int target) {
+        int[] result = new int[]{-1, -1};
+        if (nums.length == 0) {
+            return result;
+        }
+        int i = 0;
+        int j = nums.length - 1;
+        while (i < j) {
+            int mid = (i + j) / 2;
+            if (nums[mid] < target) {
+                i = mid + 1;
+            } else {
+                j = mid;
+            }
+        }
+        if (nums[i] != target)
+            return result;
+        result[0] = i;
+        j = nums.length - 1;
+        while (i < j) {
+            int mid = (i + j) / 2 + 1; // 中位数偏右，避免上面的判断无法跳出循环
+            if (nums[mid] > target) {
+                j = mid - 1;
+            } else {
+                i = mid;
+            }
+        }
+        if (nums[j] == target) {
+            result[1] = j;
+        }
+        return result;
+    }
+}
diff --git a/src/leetcode/_34_/solution.md b/src/leetcode/_34_/solution.md
@@ -0,0 +1,65 @@
+### [34\. Find First and Last Position of Element in Sorted ArrayCopy for Markdown](https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/)
+
+Difficulty: **Medium**
+
+
+Given an array of integers `nums` sorted in ascending order, find the starting and ending position of a given `target` value.
+
+Your algorithm's runtime complexity must be in the order of _O_(log _n_).
+
+If the target is not found in the array, return `[-1, -1]`.
+
+**Example 1:**
+
+```
+Input: nums = [5,7,7,8,8,10], target = 8
+Output: [3,4]```
+
+**Example 2:**
+
+```
+Input: nums = [5,7,7,8,8,10], target = 6
+Output: [-1,-1]```
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+class Solution {
+    public int[] searchRange(int[] nums, int target) {
+        int[] result = new int[]{-1, -1};
+        if (nums.length == 0) {
+            return result;
+        }
+        int i = 0;
+        int j = nums.length - 1;
+        while (i < j) {
+            int mid = (i + j) / 2;
+            if (nums[mid] < target) {
+                i = mid + 1;
+            } else {
+                j = mid;
+            }
+        }
+        if (nums[i] != target)
+            return result;
+        result[0] = i;
+        j = nums.length - 1;
+        while (i < j) {
+            int mid = (i + j) / 2 + 1; // 中位数偏右，避免上面的判断无法跳出循环
+            if (nums[mid] > target) {
+                j = mid - 1;
+            } else {
+                i = mid;
+            }
+        }
+        if (nums[j] == target) {
+            result[1] = j;
+        }
+        return result;
+    }
+}
+```
+![](https://ws4.sinaimg.cn/large/006tKfTcgy1g13hk8nrndj310s0r042m.jpg)
