add dynamic

alg/src/main/java/greedy/Parse.java

@@ -0,0 +1,55 @@
+package greedy;
+
+/**
+ * @author [email protected]
+ */
+public class Parse {
+    public static void main(String[] args) {
+       int[] nums = new int[] {2,3,1,1,4};
+       int [] nums2 = new int[] {3,2,1,0,4};
+       int[] nums3 = new int[] {2,0};
+       System.out.println(canJump(nums));
+       System.out.println(canJump(nums2));
+       System.out.println(canJump(nums3));
+    }
+
+
+    /**
+     * 通配符匹配，
+     * https://leetcode-cn.com/problems/wildcard-matching/description/
+     * 这题简单的做法应该就是迭代判断
+     * @param s
+     * @param p
+     * @return
+     */
+    public static boolean isMatch(String s, String p) {
+        return true;
+    }
+
+
+    /**
+     * 跳跃游戏，就是图
+     * @param nums
+     * @return
+     */
+    public static boolean canJump(int[] nums) {
+        if (nums.length <= 1) {
+            return true;
+        }
+        int i;
+        int right ;
+        int left;
+        for (i =0; i< nums.length && nums[i] !=0;) {
+            right = i + nums[i];
+            left = i + 1;
+            for (int j = i+1; j< nums.length && j<= right; j++) {
+                if (j + nums[j] >= right) {
+                    right = j + nums[j];
+                    left = j;
+                }
+            }
+            i = left;
+        }
+        return i == nums.length;
+    }
+}

alg/src/main/java/plan/Climb.java

@@ -0,0 +1,102 @@
+package plan;
+
+import java.util.Arrays;
+
+/**
+ * @author [email protected]
+ */
+public class Climb {
+    public static void main(String[] args) {
+        //System.out.println(climbStairs(4));
+       // int[] rob1 = new int[] {2,7,9,3,1};
+        //System.out.println(rob(rob1));
+        //int[] rob2 = new int[] {1,2,3,1};
+       // System.out.println(rob(rob2));
+        int[] array = new int[] {-2,1,-3,4,-1,2,1,-5,4};
+        System.out.println(maxSubArray(array));
+    }
+
+    /**
+     * 爬梯子https://leetcode-cn.com/explore/interview/card/top-interview-questions-easy/23/dynamic-programming/54/
+     * dp[n] = dp[n-2] + dp[n-1]
+     * @param n
+     * @return
+     */
+    public static int climbStairs(int n) {
+        if(n < 1) {
+            return 0;
+        }
+
+        if (n == 1) {
+            return 1;
+        }
+
+        if (n == 2) {
+            return 2;
+        }
+        int pre[] = new int [] {1,2};
+        int result = pre[0] + pre[1];
+        for (int i = 3; i <= n; i++) {
+            result = pre[0] + pre[1];
+            pre[0] = pre[1];
+            pre[1] = result;
+        }
+        return result;
+    }
+
+    /**
+     * https://leetcode-cn.com/explore/interview/card/top-interview-questions-easy/23/dynamic-programming/57/
+     * dp[i] = max(dp[i-2] + nums[i], dp[i-1])
+     * @param nums
+     * @return
+     */
+    public static int rob(int[] nums) {
+        if (nums.length ==0) {
+            return 0;
+        }
+        if (nums.length == 1) {
+            return nums[0];
+        }
+
+        if (nums.length  ==2) {
+            return Math.max(nums[0],nums[1]);
+        }
+
+        int dp[] = new int[] {nums[0], Math.max(nums[0], nums[1])};
+        int result=0;
+        for (int i = 2; i < nums.length; i++) {
+            result = Math.max(dp[0] + nums[i], dp[1]);
+            dp[0] = dp[1];
+            dp[1] = result;
+        }
+        return result;
+    }
+
+    /**
+     * dp[n] = max[dp[n-1],dp[n-1]+n,n]
+     * @param nums
+     * @return
+     */
+    public static int maxSubArray(int[] nums) {
+        if (nums.length == 0) {
+            return 0;
+        }
+
+        if (nums.length == 1) {
+            return nums[0];
+        }
+        int result = 0;
+        if (nums.length  ==2) {
+            result = Math.max(nums[0],nums[1]);
+            result = Math.max(result, nums[0] + nums[1]);
+        }
+        int dp = result;
+        for (int i = 2; i< nums.length; i++) {
+            result = Math.max(dp, dp+nums[i]);
+            result = Math.max(result, nums[i]);
+            dp = result;
+        }
+        return result;
+    }
+
+}