【字符串、栈】string转double

stod函数

将string转为double

string t = s.substr(i, j - i);
double num = stod(t);

例题：货币单位换算

样例1
输入

2
20CNY53fen
53HKD87cents

输出

6432

说明：
20元53分+53港元87港分，换算成人民币分后汇总，为6432

样例2
输入

1
100CNY

输出

10000

说明：
100CNY转换后是10000fen,所以输出结果为10000

样例3
输入

1
3000fen

输出

3000

说明：
3000fen,结果就是3000

样例4
输入

1
123HKD

输出

10000

说明：
HKD与CNY的汇率关系是123:100,所以换算后，输出结果为10000

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C++代码

#include <iostream>
#include <stack>using namespace std;
using i64 = long long;int n, sum;
stack<double> stk;double get(string &s)
{for (int i = 0; i < s.size(); i++){char x = s[i];if (isdigit(x)){int j = i;double num = 0;while (j < s.size() && isdigit(s[j])) j++;string t = s.substr(i, j - i);num = stod(t);stk.push(num);i = j - 1;}else if (isupper(x)){int j = i;string word;while (j < s.size() && isupper(s[j])) word += s[j++];double t = stk.top();stk.pop();if (word == "CNY") t *= 100;else if (word == "JPY") t = t / 1825 * 10000;else if (word == "HKD") t = t / 123 * 10000;else if (word == "EUR") t = t / 14 * 10000;else if (word == "GBP") t = t / 12 * 10000;stk.push(t);i = j - 1;}else if (islower(x)){int j = i;string word;while (j < s.size() && islower(s[j])) word += s[j++];double t = stk.top();stk.pop();if (word == "fen") t = t;else if (word == "cents") t = t / 123 * 100;else if (word == "sen") t = t / 1825 * 100;else if (word == "eurocents") t = t / 14 * 100;else if (word == "pence") t = t / 12 * 100;stk.push(t);i = j - 1;}}if (stk.size() > 1){double b = stk.top();stk.pop();double a = stk.top();stk.pop();stk.push(a + b);}return stk.top();
}int main()
{ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);cin >> n;while (n--){string s;cin >> s;sum += (int)get(s);}cout << sum;return 0;
}