check.cpp

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main() {
    char str[100];
    char ans[100];
    FILE *ansf = fdopen(2, "r");
    while(fgets(str, sizeof(str), stdin) != NULL) {
        if(fgets(ans, sizeof(ans), ansf) == NULL) {
            return -1;
        }
        if(strcmp(str, ans)) {
            return -1;
        }
    }
    if(fgets(ans, sizeof(ans), ansf) != NULL) {
        return -1;
    }
    return 0;
}

conf.json

{
    "test": [{
        "memlimit": 268435456,
        "metadata": {
            "data": [0]
        },
        "timelimit": 10000,
        "test_idx": 0
    }],
    "metadata": {
        "redir_test": {
            "pipeout": 1,
            "testin": 0,
            "testout": -1,
            "pipein": -1
        },
        "redir_check": {
            "ansin": 2,
            "testin": -1,
            "pipeout": 0,
            "pipein": -1
        }
    },
    "res_path": "res",
    "comp_type": "g++",
    "check_type": "ioredir",
    "code_path": "test.cpp",
    "chal_id": 1
}