LeetCode150-Array 基础题，数组操作

1. 合并有序数组

#include <iostream>
#include <vector>
using namespace std;

class Solution {
public:
  void swap(int &a, int &b) {
    int temp = b;
    b = a;
    a = temp;
  }
  void merge(vector<int> &nums1, int m, vector<int> &nums2, int n) {
    int i , j;
    for (i = 0, j = 0; i < m && n > 0 && j < n; i++) {
        if (nums1[i] > nums2[j]) {
            int mi = m;
            while(mi > i)
            {//s1[i] > s2[j] 全部往后移动一个,插入s2[j]
                nums1[mi] =  nums1[mi-1];
                mi--;
            }
            m = m+1;
            nums1[i] = nums2[j];
            j++;
        }
    }
    //s1 当前元素都小于 s2 把s2 补充进来
    while (j < n ) {
        nums1[i++] = nums2[j];
        j++;
    }
  }

    void merge2(vector<int> &nums1, int m, vector<int> &nums2, int n)
    {
        int i = m+n-1;
        m--;
        n--;
        while(n >= 0)
        {
            while(m>=0 && nums1[m] > nums2[n])
            {
                swap(nums1[i--],nums1[m--]);
            }
            swap(nums1[i--], nums2[n--]);
        }
    }

    void merge3(vector<int> &nums1, int m, vector<int> &nums2, int n)
    {
        int i = m-1, j = n-1, s1 = m+n-1;
        while(s1 >= 0 && i >= 0 && j >= 0)
        {
            if(nums1[i] > nums2[j])
            {
                nums1[s1] = nums1[i];
                i--;
            }
            else
            {
                nums1[s1] = nums2[j];
                j--;
            }
            s1--;
        }

        while(j >= 0 && s1 >= 0)
        {
            nums1[s1] =  nums2[j];
            s1--;
            j--;
        }
    }
};

int main() {
  vector<int> nums1 = {2,0};
  vector<int> nums2 = {1};
  int m = 1;
  int n = 1;
  Solution sol;
  sol.merge3(nums1, m, nums2, n);

  for (int i = 0; i < n + m; i++) {
    cout << nums1[i] << " ";
  }
  return 0;
}

2. 移除数组元素

class Solution {
public:
   //笨方法时间有点长
  int removeElement(vector<int> &nums, int val) {
    for (vector<int>::iterator it = nums.begin(); it != nums.end();) {
      if (*it == val)
        nums.erase(it);
      else
        it++;
    }
    return nums.size();
  }

  //左右指针解法
  int removeElement1(vector<int> &nums, int val) {
    int left = 0, right = 0;
    for (right = 0; right < nums.size(); right++) {
      if (nums[right] != val) {
        nums[left] = nums[right];
        left++;
      }
    }
    return left;
  }

  //左右指针优化
    int removeElement2(vector<int> &nums, int val) {
        int left = 0, right = nums.size();
        while (left < right) {
            if (nums[left] == val) {
                nums[left] = nums[right - 1];
                right--;
            } else {
                left++;
            }
        }
        return left;
    }
};