本地运行没问题，但交上去错了

https://www.luogu.com.cn/problem/P1957

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;

int ws(int);
void jia();
void jian();
void cheng();

int n, length;
string a;

int main() {
    cin >> n;
    while(n-- >= 0) {
        getline(cin, a);
        length = a.length();
        if(isdigit(a[0]) || a[0] == 'a')
            jia();
        else if(a[0] == 'b')
            jian();
        else if(a[0] == 'c')
            cheng();
    }
    return 0;
}

int ws(int x) {
    int w = 0;
    if(x < 0) {
        x = abs(x);
        w++;
    }
    while(x > 0) {
        x /= 10;
        w++;
    }
    return w;
}

void jia() {
    int i = 0, js = 0, bjs = 0;
    if(!isdigit(a[i]))
        i += 2;
    while(a[i] != ' ') {
        bjs *= 10;
        bjs += a[i] - '0';
        i++;
    }
    i++;
    while(i < length) {
        js *= 10;
        js += a[i] - '0';
        i++;
    }
    int h = bjs + js;
    int l = ws(bjs) + ws(js) + ws(h) + 2;
    printf("%d+%d=%d\n%d\n", bjs, js, h, l);
    return ;
}

void jian() {
    int i = 0, js = 0, bjs = 0;
    if(!isdigit(a[i]))
        i += 2;
    while(a[i] != ' ') {
        bjs *= 10;
        bjs += a[i] - '0';
        i++;
    }
    i++;
    while(i < length) {
        js *= 10;
        js += a[i] - '0';
        i++;
    }
    int h = bjs - js;
    int l = ws(bjs) + ws(js) + ws(h) + 2;
    printf("%d-%d=%d\n%d\n", bjs, js, h, l);
    return ;
}

void cheng() {
    int i = 0, cs = 0, bcs = 0;
    if(!isdigit(a[i]))
        i += 2;
    while(a[i] != ' ') {
        bcs *= 10;
        bcs += a[i] - '0';
        i++;
    }
    i++;
    while(i < length) {
        cs *= 10;
        cs += a[i] - '0';
        i++;
    }
    int h = bcs * cs;
    int l = ws(bcs) + ws(cs) + ws(h) + 2;
    printf("%d*%d=%d\n%d\n", bcs, cs, h, l);
    return ;
}

代码修改如下，供参考:

#include <cstdio>
#include <string>
#include <iostream>
#include <algorithm>
using namespace std;
int  ws(int);
void operation(string a,char ch);
int main() 
{
    int n, i = 0;
    string a;
    char ch;
    cin >> n;
    cin.get();
    while (n--) {         
        getline(cin, a);
        if (a[0] == 'a') {
            ch = '+';
        }
        else if (a[0] == 'b') {
            ch = '-';
        }
        else if (a[0] == 'c') {
            ch = '*';
        }
        else if (i == 0)
            continue;
        operation(a, ch); 
        i++;
    }
    return 0;
}
int ws(int x) {
    int w = 0;
    if (x < 0) {
        x = abs(x);
        w++;
    }
    while (x > 0) {
        x /= 10;
        w++;
    }
    return w;
}
void operation(string a,char ch)
{
    int i = 0, flg = 0, js = 0, bjs = 0, tmp = 0;
    while (i < a.length())
    {
        if (isdigit(a[i]))
        {
            flg = 1;
            while (isdigit(a[i]) && i < a.length()) {
                js = js * 10 + a[i] - '0';
                i++;
            }
        }
        if (flg == 1){
            flg = 0;
            if (bjs == 0) {
                bjs = js;
                js = 0;
            }
        }
        i++;
    }
    switch (ch) {
    case '+':
        tmp = bjs + js;
        break;
    case '-':
        tmp = bjs - js;
        break;
    case '*':
        tmp = bjs * js;
        break;
    default:
        bjs = js = 0;
        tmp = 0;
        break;
    }
    printf("%d%c%d=%d\n%d\n", bjs, ch, js, tmp, ws(bjs) + ws(js) + ws(tmp) + 2);
}

注意审题，题目说，如果某一行只有两个操作数，默认和上一行的操作一样，但是你默认按照加法做了

输出格式应该是全部输入完然后一起输出吧