function hasCharWithExactlyTwoOccurrences(line) {
    const charCounts = Array(256).fill(0); 
 
    for (let i = 0; i < line.length; i++) {
        charCounts[line.charCodeAt(i)]++; 
    }
 
    for (let i = 0; i < 256; i++) {
        if (charCounts[i] === 2) {
            return true; 
        }
    }
 
    return false; 
}
 
function filterLines(lines) {
    const result = [];
    for (let i = 0; i < lines.length; i++) {
        if (hasCharWithExactlyTwoOccurrences(lines[i])) {
            result.push(lines[i]); 
        }
    }
    return result;
}
 
// Example input
const input = [
    "asdf",
    "fdas",
    "asds",
    "d",
    "fm",
    "dfaa",
    "aaaa",
    "aabb",
    "aaabb"
];
 
const result = filterLines(input);
console.log(result);
 

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