计蒜客之字符串篇

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1. 百度的科学计算器

//浮点数分解:符号+整数部分+小数部分+字母e+符号+整数部分
#include <iostream>
#include <string>
using namespace std;

string in;

void cal1(string in, int s, int e) {
    char sign = '+';
    char c;
    int ans = 0;
    int casei = s;
    if (in[casei] == '+' || in[casei] == '-') {
        sign = in[casei];
        casei++;
    }
    while (casei <= e) {
        ans = ans * 10 + in[casei] - '0';
        casei++;
    }
    if (sign == '-' && ans) cout << sign; //ans!=0
    cout << ans;
}

void cal2(string in, int s, int e) {
    int non_zero_bit = -1;
    for (int casei = s; casei <= e; casei++) {
        if (in[casei] > '0') non_zero_bit = casei;
    }
    //0012300
    if (non_zero_bit != -1) {
        cout << '.';
        for (int casei = s; casei <= non_zero_bit; casei++) {
            cout << in[casei];
        }
    }
}

void solve1(string in, int s, int e) {
    int pos = in.find('.');
    cal1(in, 0, pos - 1);
    cal2(in, pos + 1, e);
}

void solve2(string in, int s, int e) {
    cout << 'e';
    cal1(in, s, e);
    cout << '\n';
}

int main() {
    cin >> in;
    int pos = in.find('e');
    solve1(in, 0, pos - 1);
    solve2(in, pos + 1, in.size() - 1);
    return 0;
}