P1175 学习笔记

省流：毒瘤字符串

题目传送门

没事中间加个转中缀干嘛？害的我当年调了一上午。

这个就是栈的经典板子后缀表达式的一个加强版，需要先中缀转后缀再求答案。

灵活变通，压两个栈不就行了。

中缀转后缀：

string zhongzhui(string s){
	mp['+'] = 1;
	mp['-'] = 2;
	mp['*'] = 3;
	mp['/'] = 4;
	mp['('] = 5;
	mp[')'] = 6;
	mp['^'] = 7;
	for (int i = 1; i <= 9; i++)
		for (int j = 1; j <= 9; j++)
			b[i][j] = 0;
	b[5][5] = 1; b[7][7] = 1; b[1][3] = 1; b[1][4] = 1; b[1][5] = 1; b[1][7] = 1; b[2][3] = 1; b[2][4] = 1; b[2][5] = 1;
	b[2][7] = 1; b[3][5] = 1; b[3][7] = 1; b[4][5] = 1; b[4][7] = 1; b[5][1] = 1; b[5][2] = 1; b[5][3] = 1; b[5][4] = 1;
	b[5][6] = 1; b[5][7] = 1; b[6][1] = 1; b[6][2] = 1; b[6][3] = 1; b[6][4] = 1; b[6][5] = 1; b[6][7] = 1; b[7][5] = 1; // 小小打表
	string ans;
	char a[35] = "";
	int num = 0, sum = 0;
	for (int i = 0; i < s.size(); i++)
		if (s[i] >= '0' && s[i] <= '9')
			num = num * 10 + s[i] - 48;
		else {
			if (num > 0){
				string str = "";
				while (num > 0)
					str = char(num % 10 + '0') + str, num /= 10;
				ans = ans + str + ' ';
			}
			if (s[i] == ')') // 关于括号的处理
				while(1){
					if (sum <= 0)
						break;
					if (a[sum] == '('){
						sum--;
						break;
					}
					ans = ans + a[sum] + ' ';
					sum--;
				}
			else{
				while(sum > 0 && b[mp[a[sum]]][mp[s[i]]] == 0)
					ans = ans + a[sum] + ' ', sum--;
				a[++sum] = s[i];
			}
		}
	if (num > 0){
		string str = "";
		while (num > 0)
			str = char(num % 10 + '0') + str, num /= 10;
		ans = ans + str + ' ';
	}
	while (1){
		ans = ans + a[sum] + ' ';
		sum--;
		if (sum <= 0)
			break;
	}
	return ans;
}

后缀求答案：

void getans(string s){ // 橙
    cout << s << endl;
	int x = 0, sum = 0, a[100005] = {0};
	for (int i = 0; i < s.size(); i++){
		if (s[i] >= '0' && s[i] <= '9')
			x = x * 10 + s[i] - 48;
		else if (s[i] == ' ' && x > 0)
			a[++sum] = x, x = 0;
		else{
            if (s[i] == ' ')
                continue;
			if (s[i] == '+')
				a[sum - 1] += a[sum], sum--;
			else if (s[i] == '-')
				a[sum - 1] -= a[sum], sum--;
			else if (s[i] == '*')
				a[sum - 1] *= a[sum], sum--;
			else if (s[i] == '/')
				a[sum - 1] /= a[sum], sum--;
			else if (s[i] == '^')
				a[sum - 1] = pow(a[sum - 1], a[sum]), sum--;
			for (int i = 1; i < sum; i++)
				cout << a[i] << ' ';
            cout << a[sum];
			cout << s.substr(i + 1) << endl;;
		}
	}
} 

所以橙+黄=绿。

code

#include<bits/stdc++.h>
using namespace std;

string s;
map <char, int> mp;
int b[10][10];

void getans(string s){
    cout << s << endl;
	int x = 0, sum = 0, a[100005] = {0};
	for (int i = 0; i < s.size(); i++){
		if (s[i] >= '0' && s[i] <= '9')
			x = x * 10 + s[i] - 48;
		else if (s[i] == ' ' && x > 0)
			a[++sum] = x, x = 0;
		else{
            if (s[i] == ' ')
                continue;
			if (s[i] == '+')
				a[sum - 1] += a[sum], sum--;
			else if (s[i] == '-')
				a[sum - 1] -= a[sum], sum--;
			else if (s[i] == '*')
				a[sum - 1] *= a[sum], sum--;
			else if (s[i] == '/')
				a[sum - 1] /= a[sum], sum--;
			else if (s[i] == '^')
				a[sum - 1] = pow(a[sum - 1], a[sum]), sum--;
			for (int i = 1; i < sum; i++)
				cout << a[i] << ' ';
            cout << a[sum];
			cout << s.substr(i + 1) << endl;;
		}
	}
} 

string zhongzhui(string s){
	mp['+'] = 1;
	mp['-'] = 2;
	mp['*'] = 3;
	mp['/'] = 4;
	mp['('] = 5;
	mp[')'] = 6;
	mp['^'] = 7;
	for (int i = 1; i <= 9; i++)
		for (int j = 1; j <= 9; j++)
			b[i][j] = 0;
	b[5][5] = 1; b[7][7] = 1; b[1][3] = 1; b[1][4] = 1; b[1][5] = 1; b[1][7] = 1; b[2][3] = 1; b[2][4] = 1; b[2][5] = 1;
	b[2][7] = 1; b[3][5] = 1; b[3][7] = 1; b[4][5] = 1; b[4][7] = 1; b[5][1] = 1; b[5][2] = 1; b[5][3] = 1; b[5][4] = 1;
	b[5][6] = 1; b[5][7] = 1; b[6][1] = 1; b[6][2] = 1; b[6][3] = 1; b[6][4] = 1; b[6][5] = 1; b[6][7] = 1; b[7][5] = 1;
	string ans;
	char a[35] = "";
	int num = 0, sum = 0;
	for (int i = 0; i < s.size(); i++)
		if (s[i] >= '0' && s[i] <= '9')
			num = num * 10 + s[i] - 48;
		else {
			if (num > 0){
				string str = "";
				while (num > 0)
					str = char(num % 10 + '0') + str, num /= 10;
				ans = ans + str + ' ';
			}
			if (s[i] == ')')
				while(1){
					if (sum <= 0)
						break;
					if (a[sum] == '('){
						sum--;
						break;
					}
					ans = ans + a[sum] + ' ';
					sum--;
				}
			else{
				while(sum > 0 && b[mp[a[sum]]][mp[s[i]]] == 0)
					ans = ans + a[sum] + ' ', sum--;
				a[++sum] = s[i];
			}
		}
	if (num > 0){
		string str = "";
		while (num > 0)
			str = char(num % 10 + '0') + str, num /= 10;
		ans = ans + str + ' ';
	}
	while (1){
		ans = ans + a[sum] + ' ';
		sum--;
		if (sum <= 0)
			break;
	}
	return ans;
}

int main() {
	cin >> s;
	getans(zhongzhui(s));
	return 0;
}