lettCode-Array

1   Remove Element    lintcode-172

描述： 删相同元素，反现有长度

记忆：标不同元素，反标记值

  public int removeElement(int[] a, int elem) {
         // write your code here
         int index = 0;
         for (int i = 0; i < a.length; i++) {
             if (a[i] != elem) {
                 a[index++] = a[i];
             }
         }
         return index;
     }

2 Remove Duplicates from Sorted Array 1    lintCode-100

描述：已排序，删相同，反长度

记忆：标记不同元素，反标记

 public int removeDuplicates(int[] nums) {
         // write your code here
         if (nums.length == 0) {
             return 0;
         }
         int index = 0;
         for (int i = 1; i < nums.length; i++) {
             if (nums[index] != nums[i]) {
                 nums[++index] = nums[i];
             }
         }
         return index + 1;
     }

3 Remove Duplicates from Sorted Array 2    lintCode-101

描述：已排序，删，最多两，反长度

记忆：加标记，不等标记少二，才加长

     public int removeDuplicates(int[] nums) {
         // write your code here
         if (nums.length < 2) {
             return nums.length;
         }
         int index = 2;
         for (int i = 2; i < nums.length; i++) {
             if (nums[i] != nums[index - 2]) {
                 nums[index++] = nums[i];
             }
         }
         return index;
     }
 }

4 Plus One   lintCode-407

描述：数组加一反数组

记忆：加一，进位

  public int[] plusOne(int[] digits) {
         // Write your code here
         int carries = 1;
         for (int i = digits.length - 1; i >= 0 && carries > 0; i--) {
             int sum = digits[i] + carries;
             digits[i] = sum % 10;
             carries = sum / 10;
         }

         if (carries == 0) {
             return digits;
         }

         int[] rst = new int[digits.length + 1];
         rst[0] = 1;
         for (int i = 1; i < rst.length; i++) {
             rst[i] = digits[i - 1];
         }

         return rst;
     }

5 Pascal's Triangle  杨辉三角

记忆：两数组链表，分类

 public static List<Integer> row(int rowIndex) {
         List<Integer> res = new ArrayList<Integer>();
         int temp = 1;
         for (int i = 1; i <= rowIndex; i++) {
             List<Integer> list = new ArrayList<Integer>();
             if (i == 1) {
                 list.add(0, 1);
             } else if (i == 2) {
                 list.add(0, 1);
                 list.add(1, 1);
             } else {
                 list.add(0, 1);
                 for (int k = 0; k < res.size() - 1; k++) {
                     int sum = res.get(k) + res.get(k + 1);
                     list.add(sum);
                 }
                 list.add(i - 1, 1);
             }
             res = list;
         }
         System.out.println(res);
         return res;
     }