add

5.leetcode/src/com/fanxb/common/Q240.java

@@ -0,0 +1,31 @@
+package com.fanxb.common;
+
+/**
+ * @author fanxb
+ * @date 2021-10-25-下午4:25
+ */
+public class Q240 {
+
+    public boolean searchMatrix(int[][] matrix, int target) {
+        int m = matrix.length, n = matrix[0].length;
+        if (matrix[m - 1][n - 1] < target || matrix[0][0] > target) {
+            return false;
+        }
+        int i = 0, j = n - 1;
+        while (i < m && j >= 0) {
+            if (matrix[i][j] == target) {
+                return true;
+            } else if (matrix[i][j] < target) {
+                i++;
+            } else {
+                j--;
+            }
+        }
+        return false;
+    }
+
+    public static void main(String[] args) {
+        int[][] params = {{-1, 3}};
+        System.out.println(new Q240().searchMatrix(params, 1));
+    }
+}

5.leetcode/src/com/fanxb/common/Q367.java

@@ -0,0 +1,29 @@
+package com.fanxb.common;
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.TreeSet;
+
+/**
+ * @author fanxb
+ * @date 2021-11-04-下午4:26
+ */
+public class Q367 {
+    private static Set<Integer> valSet = new HashSet<>(10000);
+
+    static {
+        Long val;
+        for (int i = 1; ; i++) {
+            val = i * (long) i;
+            if (val > Integer.MAX_VALUE) {
+                break;
+            } else {
+                valSet.add(val.intValue());
+            }
+        }
+    }
+
+    public boolean isPerfectSquare(int num) {
+        return valSet.contains(num);
+    }
+}

5.leetcode/src/com/fanxb/common/Q412.java

@@ -0,0 +1,38 @@
+package com.fanxb.common;
+
+import java.util.*;
+
+/**
+ * @author fanxb
+ * @date 2021-10-13-上午10:36
+ */
+public class Q412 {
+    private static final List<String> RES = new ArrayList<>(10000);
+
+    public List<String> fizzBuzz(int n) {
+        if (n <= RES.size()) {
+            return RES.subList(0, n);
+        }
+        for (int i = RES.size() + 1; i <= n; i++) {
+            boolean b1 = i % 3 == 0;
+            boolean b2 = i % 5 == 0;
+            if (b1 && b2) {
+                RES.add("FizzBuzz");
+            } else if (b1) {
+                RES.add("Fizz");
+            } else if (b2) {
+                RES.add("Buzz");
+            } else {
+                RES.add(String.valueOf(i));
+            }
+        }
+        return RES;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(new Q412().fizzBuzz(2));
+        System.out.println(new Q412().fizzBuzz(3));
+        System.out.println(new Q412().fizzBuzz(5));
+        System.out.println(new Q412().fizzBuzz(15));
+    }
+}

5.leetcode/src/com/fanxb/common/Q42.java

@@ -0,0 +1,75 @@
+package com.fanxb.common;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Stack;
+
+/**
+ * @author fanxb
+ * @date 2021-11-03-下午3:12
+ */
+public class Q42 {
+
+    /**
+     * 动态规划解法
+     *
+     * @param height height
+     * @return int
+     * @author fanxb
+     * @date 2021/11/3 下午3:51
+     */
+    public int trap(int[] height) {
+        int n = height.length;
+        //leftMax[i]表示第i个位左边的最高高度,rightMax同理
+        int[] leftMax = new int[n];
+        leftMax[0] = height[0];
+        int[] rightMax = new int[n];
+        rightMax[n - 1] = height[n - 1];
+        for (int i = 1; i < n; i++) {
+            leftMax[i] = Math.max(leftMax[i - 1], height[i]);
+            rightMax[n - 1 - i] = Math.max(rightMax[n - i], height[n - i - 1]);
+        }
+        int res = 0;
+        for (int i = 1; i < n - 1; i++) {
+            res += Math.min(leftMax[i], rightMax[i]) - height[i];
+        }
+        return res;
+    }
+
+    /**
+     * 单调栈解法
+     *
+     * @param height height
+     * @return int int
+     * @author fanxb
+     * @date 2021/11/3 下午4:37
+     */
+    public int trap1(int[] height) {
+        int res = 0;
+        if (height.length <= 2) {
+            return res;
+        }
+        Stack<Integer> stack = new Stack<>();
+        stack.push(0);
+        for (int i = 1; i < height.length; i++) {
+            while (!stack.isEmpty() && height[i] > height[stack.peek()]) {
+                //当前元素大于栈顶元素
+                //栈里的元素大于等于2,说明可以开始接雨水了
+                int bottom = stack.pop();
+                if (stack.isEmpty()) {
+                    break;
+                }
+                int l = stack.peek();
+                res += (Math.min(height[i], height[l]) - height[bottom]) * (i - l - 1);
+            }
+            stack.push(i);
+        }
+        return res;
+    }
+
+
+    public static void main(String[] args) {
+        System.out.println(new Q42().trap(new int[]{0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1}));
+        System.out.println(new Q42().trap1(new int[]{0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1}));
+    }
+}