leetcode刷题

Author: rpgmakervx

myutils-algorithm/src/main/java/org/easyarch/myutils/leetcode/p35/Solution1.java

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+package org.easyarch.myutils.leetcode.p35;
+
+/**
+ * Created by xingtianyu on 2018/9/4.
+ * 搜索插入位置
+ */
+public class Solution1 {
+    public static void main(String[] args) {
+        int []nums = new int[]{};
+        System.out.println(searchInsert(nums,0));
+    }
+
+    public static int searchInsert(int[] nums, int target) {
+        int right = nums.length - 1;
+        int left = 0;
+        int position = (right + left) / 2;
+        while (right >= left){
+            int mid = (right + left) / 2;
+            System.out.println("right("+right+")+left("+left+")/2 = "+"mid("+mid+")");
+            if(nums[mid] == target){
+                return mid;
+            }else if (nums[mid] > target){
+                right = mid - 1;
+                position = mid ;
+            }else{
+                left = mid + 1;
+                position = mid + 1;
+            }
+        }
+        return position;
+    }
+}

myutils-algorithm/src/main/java/org/easyarch/myutils/leetcode/p38/Solution1.java

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+package org.easyarch.myutils.leetcode.p38;
+
+/**
+ * Created by xingtianyu on 2018/9/5.
+ */
+public class Solution1 {
+    public static void main(String[] args) {
+
+    }
+}

myutils-algorithm/src/main/java/org/easyarch/myutils/leetcode/p53/Solution1.java

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+package org.easyarch.myutils.leetcode.p53;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Created by xingtianyu on 2018/9/5.
+ */
+public class Solution1 {
+
+    public static void main(String[] args) {
+        int []nums = new int[]{-1,-2,-5,1,4,-1,10,-4,-8};
+        System.out.println(maxSubArray(nums));
+    }
+
+    public static int maxSubArray(int[] nums) {
+        List<Integer> array = new ArrayList<>();
+        for (int index = 0; index < nums.length;index++){
+            int sum = nums[index];
+            array.add(sum);
+            for (int i = index + 1;i<nums.length;i++){
+                sum += nums[i];
+                array.add(sum);
+            }
+        }
+        return Collections.max(array);
+    }
+
+}

myutils-algorithm/src/main/java/org/easyarch/myutils/leetcode/p53/Solution2.java

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+package org.easyarch.myutils.leetcode.p53;
+
+/**
+ * Created by xingtianyu on 2018/9/5.
+ * 分治法,分左右计算最大连续子数组，再求左边最大子数组+右边最大子数组得到的中间子数组，再求三者之和
+ */
+public class Solution2 {
+
+    public static void main(String[] args) {
+        int []nums = new int[]{-1,-2,-5,1,4,-1,10,-4,-8};
+        System.out.println(maxSubArray(nums));
+    }
+
+    public static int maxSubArray(int[] nums) {
+        return maxSubArray(nums,0,nums.length - 1);
+    }
+
+    public static int maxSubArray(int[] nums,int left,int right){
+        if (left >= right){
+            return nums[left];
+        }
+        int mid = (left + right) / 2;
+        int lmax = maxSubArray(nums,left,mid -1);
+        int rmax = maxSubArray(nums,mid + 1,right);
+        int mmax = nums[mid];
+        int sum = mmax;
+        for (int index = mid - 1;index >= left;index--){
+            sum += nums[index];
+            mmax = Math.max(sum,mmax);
+        }
+        sum = mmax;
+        for (int index = mid + 1;index <= right; index++ ){
+            sum += nums[index];
+            mmax = Math.max(sum,mmax);
+
+        }
+        return Math.max(mmax,Math.max(lmax,rmax));
+    }
+
+}

myutils-algorithm/src/main/java/org/easyarch/myutils/leetcode/p53/Solution3.java

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+package org.easyarch.myutils.leetcode.p53;
+
+/**
+ * Created by xingtianyu on 2018/9/5.
+ * 动态规划版。动态规划的思路就是每次求解问题n，使用n-1的结果即可，在问题开始时就算出1 到n-1的结果
+ */
+public class Solution3 {
+
+    public static void main(String[] args) {
+        int []nums = new int[]{-3,9,-2,3,1,4};
+        System.out.println(maxSubArray(nums));
+    }
+
+    public static int maxSubArray(int[] nums) {
+        if (nums == null){
+            return 0;
+        }
+        if (nums.length == 0){
+            return nums[0];
+        }
+        int sum = nums[0];
+        int max = sum;
+        for (int index = 1;index<nums.length;index++){
+            sum = (sum + nums[index]) > nums[index]?(sum + nums[index]):nums[index];
+            max = sum > max?sum:max;
+        }
+        return max;
+    }
+}

myutils-algorithm/src/main/java/org/easyarch/myutils/leetcode/p58/Solution1.java

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+package org.easyarch.myutils.leetcode.p58;
+
+/**
+ * Created by xingtianyu on 2018/9/5.
+ */
+public class Solution1 {
+
+    public static void main(String[] args) {
+        System.out.println(lengthOfLastWord(" "));
+    }
+
+    public static int lengthOfLastWord(String s) {
+        if (s == null){
+            return 0;
+        }
+        if (s.trim().length() == 0){
+            return 0;
+        }
+        String[] substrings = s.split(" ");
+        String end = substrings[substrings.length - 1];
+        if (end.trim().isEmpty()){
+            return 0;
+        }
+        return end.length();
+    }
+}

myutils-algorithm/src/main/java/org/easyarch/myutils/leetcode/p66/Solution1.java

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+package org.easyarch.myutils.leetcode.p66;
+
+import java.util.Stack;
+
+/**
+ * Created by xingtianyu on 2018/9/5.
+ */
+public class Solution1 {
+
+    public static void main(String[] args) {
+        int []num = new int[]{3,2,9};
+
+        int []plus = plusOne(num);
+        for (int i:plus){
+            System.out.println(i);
+        }
+//        long i = 9876543210L + 1;
+//        System.out.println(i);
+    }
+
+    public static int[] plusOne(int[] digits) {
+        Stack<Integer> stack = new Stack<>();
+        int carray = (digits[digits.length - 1] + 1) / 10;
+        stack.push((digits[digits.length - 1] + 1) % 10);
+        for (int index = digits.length - 2;index>=0;index--){
+            stack.push((digits[index] + carray) % 10);
+            carray = (digits[index] + carray) / 10;
+        }
+        if (carray != 0){
+            stack.push(carray);
+        }
+        int []result = new int[stack.size()];
+        int index = 0;
+        while (!stack.isEmpty()){
+            result[index] = stack.pop();
+            index++;
+        }
+        return result;
+    }
+
+}