北京理工大学复试上机--2013

1、求两个数的最大公约数

示例:

输入:24 18

输出:6

#include <iostream>
#include <math.h>
using namespace std;
int main() {
    int a, b, i, j, m;
    while (cin >> a >> b) {
        m = min(a, b);
        j = 0;
        for (i = 1; i <= m; i++) {
            if (a % i == 0 && b % i == 0) {
                if (i > j) j = i;
            }
        }
        cout << j << endl;
    }
    return 0;
}

2、输入-组英文单词，按字典顺序(大写与小写字母具有相同大小写)

排序输出.

示例:

输入: Information Info Inform info Suite suite suit

输出: Info info Inform Information suit Suite suite

#include <iostream>
#include <vector>
#include <map>
#include <string>
#include <algorithm>
using namespace std;

bool cmp(string s1, string s2)
{
    for(int i = 0; i < s1.length(); i++) {
        s1[i] = tolower(s1[i]);
    }
    for(int i = 0; i < s2.length(); i++) {
        s2[i] = tolower(s2[i]);
    }
    return s1 < s2;
}

int main()
{
    int num = 0;
    string s, str;
    vector<string> v, vv;
    map<string, int> m;
    while (getline(cin, s)) {
        for (int i = 0; i < s.length(); i++) {
            if (isalpha(s[i])) str += s[i];
            if (s[i] == ' ' || i + 1 == s.length()) {
                v.push_back(str);
                str = "";
            }
        }
        sort(v.begin(), v.end(), cmp);
        for (int i = 0; i < v.size(); i++) {
            cout << v[i] << " ";
        }
        cout << endl;
        v.clear();
    }
    return 0;
}

3、编写程序:输入表达式，输出相应二叉树的先序遍历结果（干脆中缀转前缀 后缀都给出了 ，有示例）
输入: a+b*(c- -d)-e/f
输出: -+a*b-cd/ef
infix: a+b-a*((c+d)/e-f)+g
suffix: ab+acd+e/f-*-g+
prefix: +-+ab*a-/+cdefg

#include <iostream>
#include <stack>
#include <map>
#include <vector>
#include <algorithm>
using namespace std;

string toSuf(string s)
{
    map<char, int> isp, icp; //isp--in stack preority icp--in coming preority
    isp['('] = 1; isp['*'] = 5; isp['/'] = 5; isp['+'] = 3; isp['-'] = 3; isp[')'] = 6;
    icp['('] = 6; icp['*'] = 4; icp['/'] = 4; icp['+'] = 2; icp['-'] = 2; icp[')'] = 1;
    string sufstr;
    stack<char> opt; //operator
    for (int i = 0; i < s.length(); i++) {
        if (isalpha(s[i]) || (s[i] >= '0' && s[i] <= '9')) {
            sufstr += s[i];
        }
        else if (opt.empty() || icp[s[i]] > isp[opt.top()]) {
            opt.push(s[i]);
        }
        else {
            if (s[i] == ')') {
                while (opt.top() != '(') {
                    sufstr += opt.top();
                    opt.pop();
                }
                opt.pop();
            }
            else {
                while (!opt.empty() && isp[opt.top()] >= icp[s[i]]) {
                    sufstr += opt.top();
                    opt.pop();
                }
                opt.push(s[i]);
            }
        }
    }
    while (!opt.empty()) {
        sufstr += opt.top();
        opt.pop();
    }
    return sufstr;
}

string toPre(string s)
{
    map<char, int> isp, icp; //isp--in stack preority   icp--in coming preority
    isp['('] = 6; isp['*'] = 4; isp['/'] = 4; isp['+'] = 2; isp['-'] = 2; isp[')'] = 1;
    icp['('] = 1; icp['*'] = 5; icp['/'] = 5; icp['+'] = 3; icp['-'] = 3; icp[')'] = 6;
    string prestr;
    stack<char> opt; //operator
    for (int i = s.length() - 1; i >= 0; i--) {
        if (isalpha(s[i]) || (s[i] >= '0' && s[i] <= '9')) {
            prestr += s[i];
        }
        else if (opt.empty() || icp[s[i]] >= isp[opt.top()]) {
            opt.push(s[i]);
        }
        else {
            if (s[i] == '(') {
                while (opt.top() != ')') {
                    prestr += opt.top();
                    opt.pop();
                }
                opt.pop();
            }
            else {
                while (!opt.empty() && isp[opt.top()] > icp[s[i]]) {
                    prestr += opt.top();
                    opt.pop();
                }
                opt.push(s[i]);
            }
        }
    }
    while (!opt.empty()) {
        prestr += opt.top();
        opt.pop();
    }
    reverse(prestr.begin(), prestr.end());
    return prestr;
}

int main()
{
    int l;
    string s, sufstr, prestr;
    cout << "Infix:  ";
    while (getline(cin, s)) {
        sufstr = toSuf(s);
        prestr = toPre(s);
        cout << "Suffix: " << sufstr << endl
             << "Prefix: " << prestr << endl;
        cout << endl << "Infix:  ";
    }
    return 0;
}