Go

package main

import (
    "bufio"
    "fmt"
    "os"
)

func main() {
    in := bufio.NewReader(os.Stdin)
    var n, m, x int
    fmt.Fscan(in, &n, &m, &x)

    a, b := make([]int, n), 0
    ib := make(map[int]int)
    for i := 0; i < n; i++ {
        fmt.Fscan(in, &a[i])
    }
    for i := 0; i < m; i++ {
        fmt.Fscan(in, &b)
        ib[b] = i
    }

    for i := 0; i < n; i++ {
        complement := x - a[i]
        if idx, ok := ib[complement]; ok {
            fmt.Println(i, idx)
        }
    }
}

C++

#include <iostream>
#include <unordered_map>
#include <vector>
using namespace std;

int main() {
    int n, m, x;
    scanf("%d %d %d", &n, &m, &x);

    vector<int> a(n);
    unordered_map<int, int> ib;
    for (int i = 0; i < n; ++i) {
        scanf("%d", &a[i]);
    }
    for (int i = 0; i < m; ++i) {
        int b;
        scanf("%d", &b);
        ib[b] = i;
    }

    for (int i = 0; i < n; ++i) {
        int complement = x - a[i];
        if (ib.find(complement) != ib.end()) {
            printf("%d %d\n", i, ib[complement]);
        }
    }

    return 0;
}