update 053 java

yennanliu · Dec 11, 2023 · eeb5747 · eeb5747
1 parent b0d99a5
commit eeb5747
Show file tree

Hide file tree

Showing 4 changed files with 105 additions and 11 deletions.
diff --git a/data/progress.txt b/data/progress.txt
@@ -1,4 +1,4 @@
-20231211: 39
+20231211: 39,53
 20231208: 33
 20231206: 19,003
 20231205: 23

diff --git a/data/to_review.txt b/data/to_review.txt
@@ -1,26 +1,26 @@
-2024-02-04 -> ['39']
+2024-02-04 -> ['39,53']
 2024-01-30 -> ['19,003']
 2024-01-29 -> ['23']
 2024-01-28 -> ['55,45']
-2024-01-14 -> ['39']
+2024-01-14 -> ['39,53']
 2024-01-09 -> ['19,003']
 2024-01-08 -> ['23']
 2024-01-07 -> ['55,45']
 2024-01-02 -> ['452,406,135']
-2024-01-01 -> ['39']
+2024-01-01 -> ['39,53']
 2023-12-31 -> ['134']
 2023-12-28 -> ['53']
 2023-12-27 -> ['19,003']
 2023-12-26 -> ['23']
 2023-12-25 -> ['55,45']
-2023-12-24 -> ['39']
-2023-12-19 -> ['39', '19,003']
+2023-12-24 -> ['39,53']
+2023-12-19 -> ['39,53', '19,003']
 2023-12-18 -> ['23']
 2023-12-17 -> ['55,45']
-2023-12-16 -> ['39']
-2023-12-14 -> ['39', '19,003']
-2023-12-13 -> ['39', '23']
-2023-12-12 -> ['39', '55,45', '452,406,135']
+2023-12-16 -> ['39,53']
+2023-12-14 -> ['39,53', '19,003']
+2023-12-13 -> ['39,53', '23']
+2023-12-12 -> ['39,53', '55,45', '452,406,135']
 2023-12-11 -> ['19,003']
 2023-12-10 -> ['23', '134']
 2023-12-09 -> ['19,003', '55,45']

diff --git a/leetcode_java/src/main/java/LeetCodeJava/Greedy/MaximumSubarray.java b/leetcode_java/src/main/java/LeetCodeJava/Greedy/MaximumSubarray.java
@@ -5,9 +5,48 @@
 public class MaximumSubarray {
 
     // V0
+    // IDEA : BRUTE FORCE + SUB ARRAY
+    public int maxSubArray(int[] nums) {
+
+        if (nums == null || nums.length == 0){
+            return 0;
+        }
+
+        if (nums.length == 1){
+            return nums[0];
+        }
+
+        int cumsum = 0;
+        int maxSum = -1 * Integer.MAX_VALUE;
+
+        for (int i = 0; i < nums.length; i++){
+            int cur = nums[i];
+            // NOTE !!! only add cur if cumsum + cur >= 0
+            //          -> e.g. add cur element to cur sub array
+            if (cumsum + cur >= 0){
+                cumsum = cumsum + cur;
+                maxSum = Math.max(maxSum, cumsum);
+            /**
+             *  NOTE !!!
+             *      need to consider "negative all input cases" (Math.max(maxSum, cur);)
+             *      e.g.  nums = [-1, -2]
+             *      -> so we get max between maxSum and cur
+             *      -> since whatever sub array sum in this case is < 0
+             *      -> so we choose the "biggest" negative element in nums
+             */
+            }else{
+                maxSum = Math.max(maxSum, cur);
+                cumsum = 0;
+            }
+        }
+
+        return maxSum;
+    }
+
+    // V0'
     // IDEA : BRUTE FORCE
     // https://www.bilibili.com/video/BV1aY4y1Z7ya/?share_source=copy_web&vd_source=49348a1975630e1327042905e52f488a
-    public int maxSubArray(int[] nums) {
+    public int maxSubArray_(int[] nums) {
 
         if (nums.length == 0 || nums == null){
             return 0;

diff --git a/leetcode_java/src/main/java/dev/Test1.java b/leetcode_java/src/main/java/dev/Test1.java
@@ -383,5 +383,60 @@ private int getSum(List<Integer> input){
         return res;
     }
 
+    /**
+     *  exp 1
+     *      nums = [-2,1,-3,4,-1,2,1,-5,4]
+     *
+     *      sub :
+     *          [-2]
+     *          [1],  cumsum =  -2+1 < 0, remove -2, max = 1
+     *          [] cumsum = 1 + (-3) < 0, remove 1, -3, max = 1
+     *          [4], max = 4
+     *          [ 4, -1], max = 4
+     *          [4, -1, 2], max = 5
+     *          [4, -1, 2, 1], max = 6
+     *          [4, -1, 2, 1, -5], max =6
+     *          [4, -1, 2, 1, -5, -4], max = 6
+     *
+     *
+     *   exp 2
+     *
+     *      nums = [5,4,-1,7,8]
+     *
+     *      [5], max = 5
+     *      [5, 4], max = 9
+     *      [5,4,-1], max = 9
+     *      [5,4,-1, 7], max = 15
+     *      [5,4,-1, 7, 8], max = 23
+     *
+     */
+
+    // 2 pointers
+    // https://leetcode.com/problems/maximum-subarray/
+    public int maxSubArray(int[] nums) {
 
+        if (nums == null || nums.length == 0){
+            return 0;
+        }
+
+        if (nums.length == 1){
+            return nums[0];
+        }
+
+        int cumsum = 0;
+        int maxSum = -1 * Integer.MAX_VALUE;
+
+        for (int i = 0; i < nums.length; i++){
+            int cur = nums[i];
+            if (cumsum + cur >= 0){
+                cumsum = cumsum + cur;
+                maxSum = Math.max(maxSum, cumsum);
+            }else{
+                maxSum = Math.max(maxSum, cur);
+                cumsum = 0;
+            }
+        }
+
+        return maxSum;
+    }
 }