Merge branch 'master' into patch-18

tlylt · May 14, 2021 · 62d3c60 · 62d3c60
2 parents 001a4dc + bf0db08
commit 62d3c60
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diff --git a/problems/0020.有效的括号.md b/problems/0020.有效的括号.md
@@ -202,6 +202,23 @@ func isValid(s string) bool {
 }
 ```
 
+Ruby:
+```ruby
+def is_valid(strs)
+    symbol_map = {')' => '(', '}' => '{', ']' => '['}
+    stack = []
+    strs.size.times {|i|
+        c = strs[i]
+        if symbol_map.has_key?(c)
+            top_e = stack.shift
+            return false if symbol_map[c] != top_e
+        else
+            stack.unshift(c)
+        end
+    }
+    stack.empty?
+end
+```
 
 
 -----------------------

diff --git a/problems/0027.移除元素.md b/problems/0027.移除元素.md
@@ -123,6 +123,24 @@ public:
 
 
 Java：
+```java
+class Solution {
+    public int removeElement(int[] nums, int val) {
+
+        // 快慢指针
+        int fastIndex = 0;
+        int slowIndex;
+        for (slowIndex = 0; fastIndex < nums.length; fastIndex++) {
+            if (nums[fastIndex] != val) {
+                nums[slowIndex] = nums[fastIndex];
+                slowIndex++;
+            }
+        }
+        return slowIndex;
+
+    }
+}
+```
 
 Python：
 
@@ -172,4 +190,4 @@ var removeElement = (nums, val) => {
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)
 * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
-<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
+<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
diff --git a/problems/0028.实现strStr.md b/problems/0028.实现strStr.md
@@ -565,6 +565,54 @@ public:
 
 Java：
 
+```Java
+class Solution {
+    /**
+     * 基于窗口滑动的算法
+     * <p>
+     * 时间复杂度：O(m*n)
+     * 空间复杂度：O(1)
+     * 注：n为haystack的长度，m为needle的长度
+     */
+    public int strStr(String haystack, String needle) {
+        int m = needle.length();
+        // 当 needle 是空字符串时我们应当返回 0
+        if (m == 0) {
+            return 0;
+        }
+        int n = haystack.length();
+        if (n < m) {
+            return -1;
+        }
+        int i = 0;
+        int j = 0;
+        while (i < n - m + 1) {
+            // 找到首字母相等
+            while (i < n && haystack.charAt(i) != needle.charAt(j)) {
+                i++;
+            }
+            if (i == n) {// 没有首字母相等的
+                return -1;
+            }
+            // 遍历后续字符，判断是否相等
+            i++;
+            j++;
+            while (i < n && j < m && haystack.charAt(i) == needle.charAt(j)) {
+                i++;
+                j++;
+            }
+            if (j == m) {// 找到
+                return i - j;
+            } else {// 未找到
+                i -= j - 1;
+                j = 0;
+            }
+        }
+        return -1;
+    }
+}
+```
+
 ```java
 // 方法一
 class Solution {

diff --git a/problems/0055.跳跃游戏.md b/problems/0055.跳跃游戏.md
@@ -107,7 +107,19 @@ class Solution {
 ```
 
 Python：
-
+```python
+class Solution:
+    def canJump(self, nums: List[int]) -> bool:
+        cover = 0
+        if len(nums) == 1: return True
+        i = 0
+        # python不支持动态修改for循环中变量,使用while循环代替
+        while i <= cover:
+            cover = max(i + nums[i], cover)
+            if cover >= len(nums) - 1: return True
+            i += 1
+        return False
+```
 
 Go：
 

diff --git a/problems/0056.合并区间.md b/problems/0056.合并区间.md
@@ -137,7 +137,35 @@ public:
 
 
 Java：
+```java
+class Solution {
+    public int[][] merge(int[][] intervals) {
+        List<int[]> res = new LinkedList<>();
+        Arrays.sort(intervals, new Comparator<int[]>() {
+            @Override
+            public int compare(int[] o1, int[] o2) {
+                if (o1[0] != o2[0]) {
+                    return Integer.compare(o1[0],o2[0]);
+                } else {
+                    return Integer.compare(o1[1],o2[1]);
+                }
+            }
+        });
 
+        int start = intervals[0][0];
+        for (int i = 1; i < intervals.length; i++) {
+            if (intervals[i][0] > intervals[i - 1][1]) {
+                res.add(new int[]{start, intervals[i - 1][1]});
+                start = intervals[i][0];
+            } else {
+                intervals[i][1] = Math.max(intervals[i][1], intervals[i - 1][1]);
+            }
+        }
+        res.add(new int[]{start, intervals[intervals.length - 1][1]});
+        return res.toArray(new int[res.size()][]);
+    }
+}
+```
 
 Python：
 
@@ -151,4 +179,4 @@ Go：
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)
 * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
-<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
+<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
diff --git a/problems/0070.爬楼梯完全背包版本.md b/problems/0070.爬楼梯完全背包版本.md
@@ -127,7 +127,23 @@ public:
 
 
 Java：
+```java
+class Solution {
+    public int climbStairs(int n) {
+        int[] dp = new int[n + 1];
+        int[] weight = {1,2};
+        dp[0] = 1;
+
+        for (int i = 0; i <= n; i++) {
+            for (int j = 0; j < weight.length; j++) {
+                if (i >= weight[j]) dp[i] += dp[i - weight[j]];
+            }
+        }
 
+        return dp[n];
+    }
+}
+```
 
 Python：
 
@@ -141,4 +157,4 @@ Go：
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)
 * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
-<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
+<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
diff --git a/problems/0098.验证二叉搜索树.md b/problems/0098.验证二叉搜索树.md
@@ -254,6 +254,19 @@ public:
 
 
 Java：
+```java
+class Solution {
+    public boolean isValidBST(TreeNode root) {
+        return isValidBST_2(root, Long.MIN_VALUE, Long.MAX_VALUE);
+    }
+
+    public boolean isValidBST_2 (TreeNode root, long lo, long hi) {
+        if (root == null) return true;
+        if (root.val >= hi || root.val <= lo) return false;
+        return isValidBST_2(root.left,lo,root.val) && isValidBST_2(root.right,root.val,hi);
+    }
+}
+```
 
 
 Python：
@@ -286,4 +299,4 @@ func isBST(root *TreeNode, min, max int) bool {
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)
 * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
-<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
+<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
diff --git a/problems/0101.对称二叉树.md b/problems/0101.对称二叉树.md
@@ -254,7 +254,94 @@ public:
 ## 其他语言版本
 
 Java：
+```java
+public class N0101 {
+    /**
+     * 解法1：DFS，递归。
+     */
+    public boolean isSymmetric2(TreeNode root) {
+        if (root == null) {
+            return false;
+        }
+
+        return compare(root.left, root.right);
+    }
+
+    private boolean compare(TreeNode left, TreeNode right) {
+        if (left == null && right == null) {
+            return true;
+        }
+        if (left != null && right == null) {
+            return false;
+        }
+        if (left == null && right != null) {
+            return false;
+        }
+
+        if (left.val == right.val) {
+            return compare(left.left, right.right) && compare(left.right, right.left);
+        }
+
+        return false;
+    }
+
+    /**
+     * 解法2：DFS，迭代
+     */
+    public boolean isSymmetric3(TreeNode root) {
+        if (root == null) {
+            return false;
+        }
+
+        if (!equal(root.left, root.right)) {
+            return false;
+        }
+
+        Deque<TreeNode> st = new LinkedList<>();
+
+        st.push(root.right);
+        st.push(root.left);
+
+        TreeNode curR = root.right;
+        TreeNode curL = root.left;
 
+        while (!st.isEmpty()) {
+            curL = st.pop();
+            curR = st.pop();
+
+            // 前序，处理
+            if (!equal(curL, curR)) {
+                return false;
+            }
+
+            if (curR != null && curL != null) {
+                st.push(curL.right);
+                st.push(curR.left);
+                st.push(curR.right);
+                st.push(curL.left);
+            }
+        }
+
+        return true;
+    }
+
+    private boolean equal(TreeNode l, TreeNode r) {
+        if (l == null && r == null) {
+            return true;
+        }
+        if (l != null && r == null) {
+            return false;
+        }
+        if (l == null && r != null) {
+            return false;
+        }
+        if (l.val == r.val) {
+            return true;
+        }
+        return false;
+    }
+}
+```
 
 Python：
 
@@ -283,4 +370,4 @@ const check = (leftPtr, rightPtr) => {
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)
 * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
-<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
+<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>