diff --git a/src/main/java/cn/whaifree/redo/redo_all_240721/LeetCode452.java b/src/main/java/cn/whaifree/redo/redo_all_240721/LeetCode452.java
new file mode 100644
index 0000000..0287fa4
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redo_all_240721/LeetCode452.java
@@ -0,0 +1,56 @@
+package cn.whaifree.redo.redo_all_240721;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Comparator;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/8/8 21:46
+ * @注释
+ */
+public class LeetCode452 {
+
+    @Test
+    public void test()
+    {
+        // [[10,16],[2,8],[1,6],[7,12]]
+        int[][] points = new int[][]{{10,16},{2,8},{1,6},{7,12}};
+//        System.out.println(findMinArrowShots(points));
+        // [[-2147483646,-2147483645],[2147483646,2147483647]]
+        int[][] points1 = new int[][]{{-2147483646,-2147483645},{2147483646,2147483647}};
+        System.out.println(findMinArrowShots(points1));
+        System.out.println(-2147483645-2147483647);
+    }
+
+    public int findMinArrowShots(int[][] points)
+    {
+        Arrays.sort(points, new Comparator<int[]>() {
+            @Override
+            public int compare(int[] o1, int[] o2) {
+                return o1[1] < o2[1] ? -1 : 1;
+//                if (o1[1]<o2[1])return -1;
+//                return 1;
+            }
+        });
+
+        /**
+         * |   |
+         *   | |
+         *    |     |
+         *       |      |
+         */
+        int end = points[0][1];
+        int arrows = 1;
+        for (int i = 1; i < points.length; i++) {
+            int nextStart = points[i][0];
+            if (end < nextStart) {
+                end = points[i][1];
+                arrows++;
+            }
+        }
+        return arrows;
+    }
+}
diff --git a/src/main/java/cn/whaifree/redo/redo_all_240721/LeetCode738.java b/src/main/java/cn/whaifree/redo/redo_all_240721/LeetCode738.java
new file mode 100644
index 0000000..99317a0
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redo_all_240721/LeetCode738.java
@@ -0,0 +1,63 @@
+package cn.whaifree.redo.redo_all_240721;
+
+import org.junit.Test;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/8/8 22:21
+ * @注释
+ */
+public class LeetCode738 {
+    @Test
+    public void test()
+    {
+        Solution solution = new Solution();
+
+        System.out.println(solution.monotoneIncreasingDigits(13211432));
+        System.out.println(solution.monotoneIncreasingDigits(299999));
+        System.out.println(solution.monotoneIncreasingDigits(555555));
+        System.out.println(solution.monotoneIncreasingDigits(23456));
+        System.out.println(solution.monotoneIncreasingDigits(1254321));
+        System.out.println(solution.monotoneIncreasingDigits(332));
+
+        System.out.println(Integer.parseInt("0999"));
+
+    }
+
+    class Solution {
+        /**
+         * 13211432
+         * 09999999
+         *
+         * 5432
+         * 4999
+         * @param n
+         * @return
+         */
+        public int monotoneIncreasingDigits(int n) {
+            String s = String.valueOf(n);
+            byte[] bytes = s.getBytes();
+            int start = Integer.MAX_VALUE;
+            for (int i = bytes.length - 1; i > 0; i--) {
+                byte after = bytes[i];
+                byte before = bytes[i - 1];
+                if (after < before) {
+                    bytes[i - 1] -= 1;
+                    start = i;
+                }
+            }
+
+            if (start == Integer.MAX_VALUE) {
+                return n;
+            }
+
+            for (int i = start; i < bytes.length; i++) {
+                bytes[i] = '9';
+            }
+
+            return Integer.parseInt(new String(bytes));
+        }
+
+    }
+}
diff --git a/src/main/java/cn/whaifree/redo/redo_all_240721/LeetCode763.java b/src/main/java/cn/whaifree/redo/redo_all_240721/LeetCode763.java
new file mode 100644
index 0000000..8743efe
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redo_all_240721/LeetCode763.java
@@ -0,0 +1,56 @@
+package cn.whaifree.redo.redo_all_240721;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/8/8 22:07
+ * @注释
+ */
+public class LeetCode763 {
+
+    @Test
+    public void test()
+    {
+        String s = "ababcbacadefegdehijhklij";
+        System.out.println(new Solution().partitionLabels(s));
+    }
+
+    class Solution {
+        /**
+         * 获取每个byte最后出现的地方
+         *
+         * 挨个遍历，直到索引的地方不是最后出现的地方，就截取。
+         *      每次需要找到当前比遍历中最远到哪了
+         *
+         * @param s
+         * @return
+         */
+        public List<Integer> partitionLabels(String s) {
+            byte[] bytes = s.getBytes();
+            int[] index = new int[26];
+            for (int i = 0; i < bytes.length; i++) {
+                index[bytes[i] - 97] = i;
+            }
+
+            List<Integer> res = new ArrayList<>();
+            int start = 0;
+            int rightMax = 0;
+            for (int i = 0; i < bytes.length; i++) {
+                byte aByte = bytes[i];
+                int ind = index[aByte - 97];
+                rightMax = Math.max(rightMax, ind); // 当前最右边界
+                if (ind == i && i == rightMax) {
+                    res.add(rightMax - start + 1);
+                    start = rightMax + 1;
+                }
+            }
+
+            return res;
+        }
+    }
+}