1065 a+b and c(64)

做得比较乱，修改多次后终于AC

#include <string>
#include <iostream>
#include <algorithm>
using namespace std;
bool cmp(string a,string b){
    if(a == b)
        return false;
    if(a[0] == '-' && b[0] == '-')
        return cmp(b.substr(1),a.substr(1));
    else if(a[0] == '-' && b[0] != '-')
        return false;
    else if(a[0] != '-' && b[0] == '-')
        return true;
    else{
        if(a.size() > b.size() || a.size() == b.size() && a > b)
            return true;
        else
            return false;
    }
}
string add(string a,string b){
    int c(0),i;
    string ret;
    reverse(a.begin(),a.end());
    reverse(b.begin(),b.end());
    for(i = 0;i < a.size() && i < b.size();i++){
        ret += (a[i] - '0' + b[i] - '0' + c) % 10 + '0';
        c = (a[i] - '0' + b[i] - '0' + c) / 10;
    }
    for(;i < a.size();i++){
        ret += (a[i] - '0' + c) % 10 + '0';
        c = (a[i] - '0' + c) / 10;
    }
    for(;i < b.size();i++){
        ret += (b[i] - '0' + c) % 10 + '0';
        c = (b[i] - '0' + c) / 10;
    }
    if(c != 0)
        ret += c + '0';
    reverse(ret.begin(),ret.end());
    return ret;
}
string cut(string a,string b){
    bool pos;
    if(a[0] == '-'){
        pos = false;
        a = a.substr(1);
    }
    else{
        pos = true;
        b = b.substr(1);
    }
    reverse(a.begin(),a.end());
    reverse(b.begin(),b.end());
    int c(0),i;
    string ret;
    for(i = 0;i < a.size() && i < b.size();i++){
        if(a[i] - '0' >= b[i] - '0' + c){
            ret += a[i] - b[i] - c + '0';
            c = 0;
        }
        else{
            ret += a[i] - b[i] + 10 - c + '0';
            c = 1;
        }
    }
    for(;i < a.size();i++){
        if(a[i] - '0' >= c){
            ret += a[i] - '0' - c + '0';
            c = 0;
        }
        else{
            ret += a[i] - '0' + 10 - c + '0';
            c = 1;
        }
    }
    i = ret.size() - 1;
    while(ret[i] == '0'){
        i--;
    }
    ret = ret.substr(0,i+1);
    if(!pos) ret += '-';
    reverse(ret.begin(),ret.end());
    return ret;
}
int main(){
    int n;
    scanf("%d",&n);
    for(int i = 0;i < n;i++){
        string a,b,c;
        cin >> a >> b >> c;
        if(a[0] != '-' && b[0] != '-'){
            if(cmp(add(a,b),c))
                printf("Case #%d: true
",i+1);
            else
                printf("Case #%d: false
",i+1);
        }
        else if(a[0] == '-' && b[0] == '-'){
            if(c[0] != '-')
                printf("Case #%d: false
",i+1);
            else if(cmp(c.substr(1),add(a.substr(1),b.substr(1))))
                printf("Case #%d: true
",i+1);
            else
                printf("Case #%d: false
",i+1);
        }
        else if(a[0] == '-' && b[0] != '-'){
            if(cmp(a.substr(1),b)){
                if(cmp(cut(a,b),c)) printf("Case #%d: true
",i+1);
                else printf("Case #%d: false
",i+1);
            }
            else{
                if(cmp(cut(b,a),c)) printf("Case #%d: true
",i+1);
                else printf("Case #%d: false
",i+1);
            }
        }
        else{
            if(cmp(a,b.substr(1))){
                if(cmp(cut(a,b),c)) printf("Case #%d: true
",i+1);
                else printf("Case #%d: false
",i+1);
            }
            else{
                if(cmp(cut(b,a),c)) printf("Case #%d: true
",i+1);
                else printf("Case #%d: false
",i+1);
            }
        }
    }
    return 0;
}