Merge remote-tracking branch 'upstream/master' into chenxiaoxu

Author: cxxly

Zhengyingying/src/com/zyy/week11/_303_RangeSumQueryImmutable.java

@@ -0,0 +1,31 @@
+package com.zyy.week11;
+
+/**
+ * 
+ * @author ZYY 计算nums中从i到j的数组中元素之和,但会多次调用。
+ *
+ */
+public class _303_RangeSumQueryImmutable {
+	private int[] nums;
+
+	public _303_RangeSumQueryImmutable(int[] nums) {
+		for (int i = 1; i < nums.length; i++) {
+			nums[i] = nums[i] + nums[i - 1];
+		}
+		this.nums = nums;
+	}
+
+	public int _303_RangeSumQueryImmutable(int i, int j) {
+		if (i == 0)
+			return nums[j];
+		else
+			return nums[j] - nums[i - 1];
+	}
+
+	public static void main(String[] args) {
+		int[] nums = new int[] { -2, 0, 3, -5, 2, -1 };
+		_303_RangeSumQueryImmutable rsqi = new _303_RangeSumQueryImmutable(nums);
+		int sum = rsqi._303_RangeSumQueryImmutable(0,5);
+		System.out.println(sum);
+	}
+}

Zhengyingying/src/com/zyy/week11/_307_RangeSumQueryMutable.java

@@ -0,0 +1,83 @@
+package com.zyy.week11;
+
+public class _307_RangeSumQueryMutable {
+	// 9.57%
+	class SegmentTreeNode {
+		// 记录分段的起始位置
+		int start, end;
+		SegmentTreeNode left, right;
+		int sum;
+
+		// 初始化
+		SegmentTreeNode(int start, int end) {
+			this.start = start;
+			this.end = end;
+			this.left = null;
+			this.right = null;
+			this.sum = 0;
+		}
+	}
+
+	SegmentTreeNode root = null;
+
+	public _307_RangeSumQueryMutable(int[] nums) {
+		root = buildTree(nums, 0, nums.length - 1);
+	}
+
+	private SegmentTreeNode buildTree(int[] nums, int start, int end) {
+		if (start > end)
+			return null;
+		// 初始化一个节点
+		SegmentTreeNode ret = new SegmentTreeNode(start, end);
+		if (start == end)
+			ret.sum = nums[start];
+		else {
+			int mid = start + (end - start) / 2;
+			ret.left = buildTree(nums, start, mid);
+			ret.right = buildTree(nums, mid + 1, end);
+			ret.sum = ret.left.sum + ret.right.sum;
+		}
+		return ret;
+
+	}
+
+	void update(int i, int val) {
+		update(root, i, val);
+	}
+
+	// 更新需要先找到这个点的位置，采用二分搜索
+	private void update(SegmentTreeNode node, int index, int val) {
+		// 只有这一个节点,更新值
+		if (node.start == node.end)
+			node.sum = val;
+		else {
+			int mid = node.start + (node.end - node.start) / 2;
+			if (index <= mid)
+				update(node.left, index, val);
+			else
+				update(node.right, index, val);
+			// 需要更新当前节点的sum值
+			node.sum = node.left.sum + node.right.sum;
+		}
+	}
+
+	public int sumRange(int i, int j) {
+		return sumRange(root, i, j);
+	}
+
+	private int sumRange(SegmentTreeNode node, int start, int end) {
+		if (node.start == start && node.end == end)
+			return node.sum;
+		else {
+			int mid = node.start + (node.end - node.start) / 2;
+			if (end <= mid) {
+				return sumRange(node.left, start, end);
+			} else if (start >= mid + 1) {
+				return sumRange(node.right, start, end);
+			} else
+				return sumRange(node.left, start, mid)
+						+ sumRange(node.right, mid + 1, end);
+		}
+
+	}
+}

Zhengyingying/src/com/zyy/week11/_307_RangeSumQueryMutable_1.java

@@ -0,0 +1,47 @@
+package com.zyy.week11;
+
+//75.38% 7ms
+public class _307_RangeSumQueryMutable_1 {
+	// 使用树状数组
+	private int[] BIT;
+	private int[] nums;
+	private int n;
+
+	public _307_RangeSumQueryMutable_1(int[] nums) {
+		this.n = nums.length;
+		this.BIT = new int[n + 1];
+		this.nums = nums;
+		for (int i = 0; i < n; i++) {
+			init(i, nums[i]);
+		}
+	}
+
+	private void init(int pos, int val) {
+		pos++;
+		while (pos <= n) {
+			BIT[pos] += val;
+			pos += pos & -pos;
+		}
+	}
+
+	void update(int i, int val) {
+		int discard = val - nums[i];
+		nums[i] = val;
+		init(i, discard);
+	}
+
+	int getSum(int i) {
+		i++;
+		int sum = 0;
+		while (i > 0) {
+			sum += BIT[i];
+			i -= i & -i;
+		}
+		return sum;
+	}
+
+	public int sumRange(int i, int j) {
+		return getSum(j) - getSum(i - 1);
+	}
+
+}