题目链接
将中缀表达式转化为后缀表达式。
数字的话直接放到答案的字符串里。
如果是左括号就进栈， 右括号就让栈里的符号都出来直到第一个左括号。
否则的话比较当前符号的优先级和栈顶符号的优先级。
#include <iostream>
#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <complex>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <queue>
#include <stack>
#include <bitset>
using namespace std;
#define pb(x) push_back(x)
#define ll long long
#define mk(x, y) make_pair(x, y)
#define lson l, m, rt<<1
#define mem(a) memset(a, 0, sizeof(a))
#define rson m+1, r, rt<<1|1
#define mem1(a) memset(a, -1, sizeof(a))
#define mem2(a) memset(a, 0x3f, sizeof(a))
#define rep(i, n, a) for(int i = a; i<n; i++)
#define fi first
#define se second
typedef complex <double> cmx;
typedef pair<int, int> pll;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int mod = 1e9+7;
const int inf = 1061109567;
const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
map <char, int> sign;
vector <char> ans;
void solve() {
ans.clear();
stack <char> st;
string s;
cin>>s;
int last = 6;
for(int i = 0; i < s.size(); i++) {
char c = s[i];
if(isalnum(c)) {
ans.pb(c);
} else {
if(c == '(') {
st.push(c);
last = 6;
} else if(c == ')') {
char tmp;
tmp = st.top();
st.pop();
do {
ans.pb(tmp);
tmp = st.top();
st.pop();
} while (tmp != '(');
last = 6;
} else {
if(sign[c]>=last) {
ans.pb(c);
} else {
st.push(c);
last = sign[c];
}
}
}
}
for(auto &i: ans) {
cout<<i;
}
cout<<endl;
}
void init() {
sign['+'] = 1;
sign['-'] = 2;
sign['*'] = 3;
sign['/'] = 4;
sign['^'] = 5;
}
int main()
{
init();
int t;
cin>>t;
while(t--) {
solve();
}
return 0;
}