Create RangeSumQueryMutable.java

Author: leo414

RangeSumQueryMutable.java

@@ -0,0 +1,93 @@
+package leetcode;
+
+import java.util.Arrays;
+
+/**
+ * Project Name : Leetcode
+ * Package Name : leetcode
+ * File Name : RangeSumQueryMutable
+ * Creator : Leo
+ * Description : 307. Range Sum Query - Mutable
+ */
+public class RangeSumQueryMutable {
+
+    int[] nums;
+    int[] tree;
+    int n;
+
+    // time : O(n * logn)
+    public RangeSumQueryMutable(int[] nums) {
+        n = nums.length;
+        tree = new int[n + 1];
+        this.nums = new int[n];
+        for (int i = 0; i < n; i++) {
+            update(i, nums[i]);
+        }
+    }
+
+    // time : O(logn)
+    public void update(int i, int val) {
+        if (n == 0) return;
+        int diff = val - nums[i];
+        nums[i] = val;
+        for (int j = i + 1; j <= n; j += j & (-j)) {
+            tree[j] += diff;
+        }
+    }
+
+    // time : O(logn)
+    public int sumRange(int i, int j) {
+        return sum(j + 1) - sum(i);
+    }
+
+    private int sum(int k) {
+        int sum = 0;
+        for (int i = k; i > 0; i -= i & (-i)) {
+            sum += tree[i];
+        }
+        return sum;
+    }
+
+    /**
+     * 解法2
+     */
+    //private int[] tree;
+    //private int[] nums;
+
+    public void NumArray(int[] nums) {
+        this.nums = nums;
+        int sum;
+        int lowbit;
+        tree = new int[nums.length + 1];
+        for (int i = 1; i < tree.length; i++) {
+            sum = 0;
+            lowbit = i & (-i);
+            for (int j = i; j > i - lowbit; j--) {
+                sum = sum + nums[j - 1];
+            }
+            tree[i] = sum;
+        }
+    }
+
+    public void update2(int i, int val) {
+        int diff = val - nums[i];
+        nums[i] = val;
+        i++;
+        for (; i < tree.length; i += (i & (-i))) {
+            tree[i] += diff;
+        }
+    }
+
+    public int sumRange2(int i, int j) {
+        return sum2(j + 1) - sum2(i);
+    }
+
+    private int sum2(int k) {
+        int sum = 0;
+        for (int i = k; i > 0; i -= i & (-i)) {
+            sum += tree[i];
+        }
+        return sum;
+    }
+
+}