Acwing语法基础

862. 三元组排序 - AcWing题库

#include<iostream>
#include<algorithm>
#include<string>
using namespace std;
struct Triple{
    int x;
    float y;
    string z;
};
bool Compare(Triple a,Triple b){
    return a.x<b.x;
}

int main(){
    int N;
    cin>>N;
    Triple arr[N];
    for(int i=0;i<N;i++){
        cin>>arr[i].x>>arr[i].y>>arr[i].z;
    }
    sort(arr,arr+N,Compare);
    for(int i=0;i<N;i++){
        printf("%d %.2f %s \n",arr[i].x,arr[i].y,arr[i].z.c_str());
        //注意printf()的用法
        //用s.c_str()将string转化为char *s
    }
}

67. 数字在排序数组中出现的次数 - AcWing题库

//for each
class Solution {
public:
    int getNumberOfK(vector<int>& nums , int k) {
        int cnt=0;
        for(int x:nums){
            if(x==k){
                cnt++;
            }
        }
        return cnt;
        
    }
};

//迭代器
class Solution {
public:
    int getNumberOfK(vector<int>& nums , int k) {
        int cnt=0;
        vector<int>::iterator it;
        for(it=nums.begin();it!=nums.end();it++){
            if(*it==k) cnt++;
        }
        return cnt;
        
    }
};
// *a.eng()=a[n];
// *a.back()=a[n-1];
// *a.begin()=*a.front()=a[0];

32. 调整数组顺序使奇数位于偶数前面 - AcWing题库

class Solution {
public:
    void reOrderArray(vector<int> &array) {
       int l=0,r=array.size()-1;
        //array.size();
       while(l<r){
           while((l<r)&&array[l]%2==1) l++;
           while((l<r)&&array[r]%2==0) r--;
           if(l<r) swap(array[l],array[r]);
       }
    }
};

17. 从尾到头打印链表 - AcWing题库

class Solution {
public:
    vector<int> printListReversingly(ListNode* head) {
        vector<int> res;
        while(head){
            res.push_back(head->val);
            head=head->next;
        }
        return vector<int>(res.rbegin(),res.rend());
        //rbegin(),rend()反向迭代器；
    }
};

class Solution {
public:
    vector<int> getLeastNumbers_Solution(vector<int> input, int k) {
        int n=input.size();
        sort(input.begin(),input.end());
        vector<int> res;
        for(int i=0;i<k;i++){
            res.push_back(input[i]);
        }
        return res;
    }
};

class Solution {
public:
    vector<int> getLeastNumbers_Solution(vector<int> input, int k) {
        int n=input.size();
        sort(input.begin(),input.end());
        vector<int> res;
        vector<int>::iterator it;
        for(it=input.begin();it<input.begin()+k;it++){//不能写it<k
            res.push_back(*it);
        }
        return res;
    }
};

vector也可以用a[i]

75. 和为S的两个数字 - AcWing题库

class Solution {
public:
    vector<int> findNumbersWithSum(vector<int>& nums, int target) {
        set<int> s;
        for(int i=0;i<nums.size();i++){
            int find=target-nums[i];
            if(s.count(find)!=0) return vector<int>{find,nums[i]};
            //int n=target-nums[i];
            //if(s.find(n)!=s.end()) return vector<int>{n,nums[i]};
            s.insert(nums[i]);
        }
        return vector<int>();
    }
};