算法竞赛入门经典 第二版 习题5-11 更新字典 Updating a Dictionary uva12504

题目：https://vjudge.net/problem/UVA-12504

思路：用集合的思想，旧字典与新字典的差集就是减少部分，新字典与旧字典的差集就是增加部分，新旧字典的交集中键值改变的部分就是修改部分。

注：读入时别忘单独处理空集。

代码：C++11

#include <iostream>#include <string>#include <cstring>#include <cctype>#include <cstdio>#include <set>#include <map>#include <algorithm>using namespace std;map<string, string> oridata;map<string, string> newdata;set<string> orikey;set<string> newkey;set<string> increase;set<string> decrease;set<string> change;void getdata(map<string, string> &nowdata, set<string> &nowkey){    bool keyflag = true;    getchar();    string key, value;    while(1)    {        char c;        c = getchar();        if(c=='}')        {            if(keyflag)            {                getchar();                return ;            }            nowdata[key] = value;            nowkey.insert(key);            getchar();            return ;        }        else if(c==':')        {            keyflag = !keyflag;        }        else if(c==',')        {            keyflag = !keyflag;            nowdata[key] = value;            nowkey.insert(key);            key.clear();            value.clear();        }        else if(keyflag)        {            key.push_back(c);        }        else        {            value.push_back(c);        }    }}void print(set<string> key){    bool first = true;    for(auto &t:key)    {        if(first)        {            first = false;        }        else        {            printf(",");        }        cout << t << flush;    }    cout << endl;}int main(){    int T;    cin >> T;    getchar();    while(T--)    {        oridata.clear();        newdata.clear();        orikey.clear();        newkey.clear();        increase.clear();        decrease.clear();        change.clear();        getdata(oridata, orikey);        getdata(newdata, newkey);        set_difference(newkey.begin(), newkey.end(), orikey.begin(), orikey.end(), inserter(increase, increase.begin()));        set_difference(orikey.begin(), orikey.end(), newkey.begin(), newkey.end(), inserter(decrease, decrease.begin()));        set<string> intersection;        set_intersection(orikey.begin(), orikey.end(), newkey.begin(), newkey.end(), inserter(intersection, intersection.begin()));        for(auto &t: intersection)        {            if(oridata[t]!=newdata[t])            {                change.insert(t);            }        }        if(increase.empty()&&decrease.empty()&&change.empty())        {            cout << "No changes" << endl;        }        if(!increase.empty())        {            printf("+");            print(increase);        }        if(!decrease.empty())        {            printf("-");            print(decrease);        }        if(!change.empty())        {            printf("*");            print(change);        }        cout << endl;    }    return 0;}