九度 1408 寻找表达式 (中缀转后缀)

题目描述

 

总结

1. '_' 运算符不是 a*10 + b, 而是 a*(10 or 100) + b

2. char * 与 string 的相互转化

char* = string.c_str()

string = char*

3. 中缀表达式转后者表达式 参考:http://www.cnblogs.com/xinsheng/p/3591781.html

4. 通用的中缀转后缀, 用 string 存数据比较好

 

代码 未通过九度测试

#include <iostream>
#include <stdio.h>
#include <string>
#include <string.h>
#include <algorithm>
#include <math.h>
#include <vector>
#include <deque>
#include <map>
#include <stdlib.h>
using namespace std;

string ops[3] = {" ", "+", "-"};
map<string, int> priority;
vector<vector<string> > resVec;

int n;

string i2s(int i) {
	char s[20];
	sprintf(s, "%d", i);
	string str = s;
	return str;
}

int s2i(string &str) {
	int tmp(atoi(str.c_str()));
	return tmp;
}

int calculate(vector<string> &vec) {
	vector<string> pos;
	deque<string> stack;
	
	for(int i = 0; i < vec.size(); i ++) {
		if(priority.count(vec[i]) == 0){ // is number
			pos.push_back(vec[i]);
			continue;
		}
		
		while(!stack.empty()) {
			string lastOp = stack.back();
			if(priority[vec[i]]> priority[lastOp]) {
				stack.push_back(vec[i]);
				break;		
			}else {
				pos.push_back(lastOp);
				stack.pop_back();
			}
		}
		
		// is operator
		if(stack.empty()) {
			stack.push_back(vec[i]);
			continue;
		}
		
	}
	
	while(!stack.empty()) {
		pos.push_back(stack.back());
		stack.pop_back();
	}
	
	stack.clear();
	for(int i = 0; i < pos.size(); i ++) {
		if(priority.count(pos[i]) == 0) {
			stack.push_back(pos[i]);		
		}else {
			string sec = stack.back();
			stack.pop_back();
			string fir = stack.back();
			stack.pop_back();

			if(pos[i] == "+") {
				int ret = s2i(fir) + s2i(sec);
				stack.push_back(i2s(ret));	
			}else if(pos[i] == "-") {
				int ret = s2i(fir) - s2i(sec);
				stack.push_back(i2s(ret));
			}else {
				int ret = s2i(fir)*pow(10, sec.size()) + s2i(sec);

				stack.push_back(i2s(ret));
			}
		}
	}
	return s2i(stack.back());
}


void dfs(int i, vector<string> &party) {
	if(i == n) {
		party.push_back(i2s(n));
		int val = calculate(party);
		if(val == 0)
			resVec.push_back(party);
		party.pop_back();
		return;
	}
	
	party.push_back(i2s(i));
	
	for(int j = 0; j < 3; j ++) {
		party.push_back(ops[j]);
		dfs(i+1, party);
		party.pop_back();
	}
	party.pop_back();
}
int main() {
	
	//freopen("C:\\Users\\vincent\\Dropbox\\workplacce\\joj\\test.txt", "r", stdin);
	priority["+"] = 1;
	priority["-"] = 1;
	priority[" "] = 2;
	
	while(scanf("%d", &n) != EOF) {
		vector<string> temp;
		dfs(1, temp);
		
		for(int i = 0; i < resVec.size(); i ++) {
			for(int j = 0; j < resVec[i].size(); j ++) {
				cout << resVec[i][j];
			}
			cout << endl;
		}
	}
	return 0;
}