1001 A+B Format

1001 A+B Format

Calculate a+b and output the sum in standard format -- that is, the digits must be separated into groups of three by commas (unless there are less than four digits).

Input Specification:

Each input file contains one test case. Each case contains a pair of integers a and b where −106≤a,b≤106. The numbers are separated by a space.

Output Specification:

For each test case, you should output the sum of a and b in one line. The sum must be written in the standard format.

Sample Input:

-1000000 9

Sample Output:

-999,991

思路：

当输出多行数值时，一定要注意是否有多余或缺少空行的情况

将 int 转换为 string 可以直接使用 to_string(x)

使用string 代替char数组的好处是 可以使用string自带的函数简化代码，提高效率。

代码：

#include<stdio.h>
#include<string.h>
#include<iostream>
using namespace std;
int main(){
    int a,b,sum,t=0,l;
    char s[100];
    while(scanf("%d%d",&a,&b) != -1){
        sum = a + b;
        sprintf(s, "%d", sum);
        if(s[0] == '-'){
            if(strlen(s) < 5){
                cout<<s;
            }else{
                cout<<s[0];
                l = strlen(s) - 1;
                for(int i=1; i<=l % 3; i++){
                    cout<<s[i];
                }
                if(l % 3 != 0) cout<<",";
                t = 0;
                for(int i=l % 3 + 1; i < strlen(s); i++){
                    cout<<s[i];
                    t++;
                    if(t == 3 && i != strlen(s) - 1){
                        cout<<",";
                        t = 0;
                    }
                }
            }
        }
        else{
           if(strlen(s) < 4){
               cout<<s;
           }else{
                l = strlen(s);
                for(int i=0; i<l % 3; i++){
                    cout<<s[i];
                }
                if(l % 3 != 0) cout<<",";
                t = 0;
                for(int i=l % 3; i < strlen(s); i++){
                    cout<<s[i];
                    t++;
                    if(t == 3 && i != strlen(s) - 1){
                        cout<<",";
                        t = 0;
                    }
                }
           }
        }
        cout<<endl;
    }
    return 0;
}

简化代码：

#include <iostream>
using namespace std;
int main() {
    int a, b;
    cin >> a >> b; //输入a和b
    string s = to_string(a + b); //将a+b的值转换为字符串
    if(s[0] == '-') { //处理符号
        cout << '-';
        s.erase(0, 1);
    }
    int count = 0; //用于记录当前位置
    for(int i = s.length() - 1; i >= 0; i--){ //添加逗号
        count++;
        if(count % 3 == 0 && i > 0){
            s.insert(i, ",");
        }
    }
    cout << s;
}