递归+非递归
递归：
遇到左括号是进行递归，之后返回子串的结果加到总结果中
非递归：
遇到左括号进行压栈，遇到右括号弹栈至出现一个左括号
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<string>
#include<vector>
#include<stack>
#include<bitset>
#include<cstdlib>
#include<cmath>
#include<set>
#include<list>
#include<deque>
#include<map>
#include<queue>
#include<sstream>
using namespace std;
typedef long long ll;
const double PI = acos(-1.0);
const double eps = 1e-6;
const int INF = 1000000000;
const int maxn = 100;
#define isBigC(x) ((x>='A' && x<='Z') ? true:false)
#define isSmallC(x) ((x>='a' && x<='z') ? true:false)
#define isN(x) ((x>='0' && x<='9') ? true:false)
//非递归
class Solution {
public:
int start;
string countOfAtoms(string formula) {
start = 0;
map<string ,int>strInt;
stack<pair<string,int> > sks;
while(start < formula.length()){
if(formula[start]=='('){
string tempString = formula.substr(start,1);
sks.push(pair<string ,int>(tempString,0));
start ++;
}else if(isBigC(formula[start])){
int j = start + 1;
while(isSmallC(formula[j])){
j++;
}
string subs = formula.substr(start ,j - start);
int tempInt = 0;
while(isN(formula[j])){
tempInt *= 10;
tempInt += formula[j] - '0';
j++;
}
tempInt = tempInt==0 ? 1 : tempInt;
sks.push(pair<string ,int>(subs,tempInt));
start = j;
}else if(formula[start]==')'){
int k = start + 1;
int intTemp=0;
while(isN(formula[k])){
intTemp *= 10;
intTemp += formula[k]-'0';
k++;
}
start = k;
intTemp = intTemp==0 ? 1 : intTemp;
stack<pair<string,int> > sktemp;
pair<string,int> stemp;
do{
stemp = sks.top();
stemp.second *= intTemp;
if(stemp.first!= "(")
sktemp.push(pair<string,int>(stemp.first,stemp.second));
sks.pop();
}while(stemp.first != "(");
while(!sktemp.empty()){
sks.push(sktemp.top());
sktemp.pop();
}
}
}
pair<string,int> temp1;
while(!sks.empty()){
temp1 = sks.top();
strInt[temp1.first] += temp1.second;
sks.pop();
}
map<string ,int>::iterator it;
string ret="";
for(it=strInt.begin();it!=strInt.end();it++){
ret += it->first;
stringstream stream;
if(it->second>1){
stream<<it->second;
ret += stream.str();
}
}
return ret;
}
};
//递归
/*
class Solution {
public:
int start;
string countOfAtoms(string formula) {
start = 0;
map<string,int> ret = cal(formula);
map<string,int>::iterator it;
string retS="";
for(it = ret.begin();it!=ret.end();it++){
retS += it->first;
if(it->second>1){
stringstream stream;
stream<<it->second;
retS += stream.str();
}
}
return retS;
}
map<string,int> cal(string formula){
map<string,int> strInt;
while(start < formula.length()){
if(formula[start]=='('){
start++;
map<string,int> tempMap = cal(formula);
map<string,int>::iterator it;
for(it = tempMap.begin();it!=tempMap.end();it++){
strInt[it->first] += it->second;
}
}else if(isBigC(formula[start])){
int j = start + 1;
while(isSmallC(formula[j])){
j++;
}
string subs = formula.substr(start ,j - start);
int tempInt = 0;
while(isN(formula[j])){
tempInt *= 10;
tempInt += formula[j] - '0';
j++;
}
tempInt = tempInt==0 ? 1 : tempInt;
strInt[subs] += tempInt;
start = j;
}else if(formula[start]==')'){
int k = start+1;
int intTemp=0;
while(isN(formula[k])){
intTemp *= 10;
intTemp += formula[k]-'0';
k++;
}
start = k;
map<string,int>::iterator it;
intTemp = intTemp==0 ? 1 : intTemp;
for(it = strInt.begin();it!=strInt.end();it++){
strInt[it->first] *= intTemp;
}
return strInt;
}
}
return strInt;
}
};
*/
int main()
{
string formula = "K4(ON(SO3)2)2";
Solution Solution1;
string s = Solution1.countOfAtoms(formula);
cout<<s<<endl;
return 0;
}