采用线段树进行编写update(int index, int newVal)方法

Xikl · Jan 19, 2019 · 0f10b21 · 0f10b21
1 parent d399ba0
commit 0f10b21
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diff --git a/src/main/java/com/ximo/datastructuresinaction/leetcode/solution303/NumArray2.java b/src/main/java/com/ximo/datastructuresinaction/leetcode/solution303/NumArray2.java
@@ -2,6 +2,8 @@
 
 import com.ximo.datastructuresinaction.segmenttree.SegmentTree;
 
+import java.util.Arrays;
+
 /**
  * @author xikl
  * @date 2019/1/8
@@ -12,10 +14,7 @@ public class NumArray2 {
     private SegmentTree<Integer> segmentTree;
 
     public NumArray2(int[] nums) {
-        Integer[] newNums = new Integer[nums.length];
-        for (int i = 0; i < nums.length; i++) {
-            newNums[i] = nums[i];
-        }
+        Integer[] newNums = Arrays.stream(nums).boxed().toArray(Integer[]::new);
 
         segmentTree = new SegmentTree<>(newNums, (next, prev) -> next + prev);
     }

diff --git a/src/main/java/com/ximo/datastructuresinaction/leetcode/solution307/NumArray.java b/src/main/java/com/ximo/datastructuresinaction/leetcode/solution307/NumArray.java
@@ -55,10 +55,17 @@ public int sumRange(int i, int j) {
      */
     public void update(int i, int val) {
         data[i] = val;
-        // 累加
+        // 累加 startIndex 为需要被更新的值中+1
         sumStartFromIndex(sum, data, i + 1);
     }
 
+    /**
+     * 求和
+     *
+     * @param sumArr 求和的数组
+     * @param dataArr 原始数据数组
+     * @param startIndex 其实的位置
+     */
     private void sumStartFromIndex(int[] sumArr, int[] dataArr, int startIndex) {
         for (int i = startIndex; i < sumArr.length; i++) {
             sumArr[i] = sumArr[i - 1] + dataArr[i - 1];

diff --git a/src/main/java/com/ximo/datastructuresinaction/leetcode/solution307/NumArray2.java b/src/main/java/com/ximo/datastructuresinaction/leetcode/solution307/NumArray2.java
@@ -0,0 +1,40 @@
+package com.ximo.datastructuresinaction.leetcode.solution307;
+
+import com.ximo.datastructuresinaction.segmenttree.SegmentTree;
+
+import java.util.Arrays;
+
+/**
+ * @author xikl
+ * @date 2019/1/19
+ */
+public class NumArray2 {
+
+    private SegmentTree<Integer> segmentTree;
+
+
+    public NumArray2(int[] nums) {
+        Integer[] newNums = Arrays.stream(nums).boxed().toArray(Integer[]::new);
+
+        segmentTree = new SegmentTree<>(newNums, (prev, next) -> prev + next);
+
+    }
+
+    public int sumRange(int i, int j) {
+        return segmentTree.queryRangeClose(i, j);
+    }
+
+
+    /**
+     * 更新其中的一个值
+     *
+     * @param i 需要被更新的位置
+     * @param val 新的值
+     */
+    public void update(int i, int val) {
+        segmentTree.set(i, val);
+    }
+
+
+
+}
diff --git a/src/test/java/com/ximo/datastructuresinaction/array/ArrayTest.java b/src/test/java/com/ximo/datastructuresinaction/array/ArrayTest.java
@@ -2,6 +2,8 @@
 
 import org.junit.Test;
 
+import java.util.Arrays;
+
 /**
  * @author Ximo
  * @date 2018/10/22 0:01
@@ -30,4 +32,14 @@ public void testArrToMyArray() {
         Array<Integer> array = new Array<>(arr);
         System.out.println(array);
     }
+
+
+    @Test
+    public void testIntToInteger() {
+        int[] intArray = {1, 2, 3, 4};
+
+        Integer[] integerArrays = Arrays.stream(intArray).boxed().toArray(Integer[]::new);
+        System.out.println(Arrays.toString(integerArrays));
+
+    }
 }