【C++】Vector and Map and Iterator and Two_Sum

作者：パっパっパスタ│2019-09-21 23:13:27│巴幣：8│人氣：390

vector

#include <iostream>
#include <vector>

using namespace std;

//vector:

int main(){
    vector<int> raw;
    raw.push_back(8);
    raw.push_back(7);
    raw.push_back(6);
    raw.push_back(3);
    for(vector<int>::iterator iter = raw.begin(); iter != raw.end(); iter++){
        cout << *iter << endl;

map

#include <iostream>
#include <map>
#include <string>

using namespace std;

int main(){
    map<string, string> hashmap;
    map<string, string>::iterator iter;

    hashmap.insert(pair<string, string>("r000", "ST1"));
    hashmap["r111"] = "ST2";
    hashmap["r222"] = "ST3";

    for(iter = hashmap.begin(); iter != hashmap.end(); ++iter){
        cout << iter->first << " , " << iter->second << endl;
    }

/*
r000 , ST1
r111 , ST2
r222 , ST3
*/

    iter = hashmap.find("r000");
    if(iter != hashmap.end()){
        cout << iter->second;
    }else{
        cout << "Not found!";
    }

//ST1

}

Two Sum

// Two Sum

#include <iostream>
#include <vector>
#include <map>

using namespace std;

class Solution{
public:
    vector<int> twosum(vector<int> &nums, int target){
        map <int, int> hashtable;            //store value and index
        map <int, int> :: iterator iter;     //iterator for find value
        vector <int> ansIndex(2);            //store index answer

        for(int i = 0; i < nums.size(); i++){
            iter = hashtable.find(target - nums[i]);

            if(iter != hashtable.end()){
                ansIndex[0] = iter->second;
                ansIndex[1] = i;
                return ansIndex;
            }else{
                //map only can change value, not key
                hashtable[nums[i]] = i;
            }
        }
        cout << "Not found!" << endl;
    }
};

/*
    step by step:

    i->0 == 2
    hashtable.find(9 - 7 == 2) (X) #hashtable is clear
    hashtable[2](key) = 0(value)

    i->1 == 7
    hashtable.find(9 - 7 == 2) (O)
    there is a '2' in hashtable, its value is 0!
    now i == 1 and iter is adress of '2' which in hashtable
    and iter->second is hashtable[2]'s value '0'
    so return index(0) and index(1)
*/

int main(){
    vector <int> arr;    //imput value
    arr.push_back(2);
    arr.push_back(7);
    arr.push_back(11);
    arr.push_back(15);
    int target = 9;

    Solution kkk;    //call function and print
    vector <int> point = kkk.twosum(arr , target);
    for(vector <int> :: iterator iter2 = point.begin(); iter2 != point.end(); iter2++){
        cout << "Index[ " << *iter2 << " ] " << endl;
    }
}

搞了三小時把vector map iterator還有最簡單的LeetCode第一題弄懂

我怕忘記所以先記錄起來

因為沒有每天認真寫題目思考

最近真的覺得邏輯思考能力真的在退化.....

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