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;
    }