Day 4 – Array Problem Solving Practice (JavaScript)

Today I practiced multiple array and loop-based problems to strengthen my fundamentals.

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💻 Problems Covered

• Sum of array elements
• Find max & min in array
• Count even/odd numbers
• Reverse an array
• Remove duplicates
• Search a specific element
• Sliding window sum (basic idea)
• Subarray sum calculation
• Array rotation

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🧠 Code Practice

// 1. Sum of array
let values = [1,2,3,4,5];
let result = 0;

for(let i = 0; i < values.length; i++){
    result += values[i];
}

console.log(result);


// 2. Find max
values = [1,2,3,4];
let max = values[0];

for(let i = 0; i < values.length; i++){
    if(values[i] > max){
        max = values[i];
    }
}

console.log(max);


// 3. Find min
values = [9,1,2,3,4];
let min = values[0];

for(let i = 0; i < values.length; i++){
    if(values[i] < min){
        min = values[i];
    }
}

console.log(min);


// 4. Count even / odd
values = [9,1,2,3,4];
let even = 0;
let odd = 0;

for(let i = 0; i < values.length; i++){
    if(values[i] % 2 === 0){
        even++;
    } else {
        odd++;
    }
}

console.log(even, odd);


// 5. Reverse array
values = [9,1,2,3,4];
let reversed = [];

for(let i = values.length - 1; i >= 0; i--){
    reversed.push(values[i]);
}

console.log(reversed);


// 6. Remove duplicates
values = [9,1,4,1,2,3,4];
let unique = [];

for(let i = 0; i < values.length; i++){
    if(!unique.includes(values[i])){
        unique.push(values[i]);
    }
}

console.log(unique);


// 7. Check if element exists
function findNumber(arr, num){
    for(let i = 0; i < arr.length; i++){
        if(arr[i] === num){
            return true;
        }
    }
    return false;
}


// 8. Sliding window sum (max sum)
values = [1,2,3,4];
let chunk = 3;
let maxSum = 0;

for(let i = 0; i <= values.length - chunk; i++){
    let sum = 0;

    for(let j = i; j < i + chunk; j++){
        sum += values[j];
    }

    maxSum = Math.max(maxSum, sum);
}

console.log(maxSum);


// 9. Array rotation (right rotate)
values = [1,2,3,4,5];

for(let i = 0; i < 2; i++){
    values.unshift(values.pop());
}

console.log(values);

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🧠 What I Learned

• Basic array traversal using loops
• Difference between max/min logic
• Using nested loops for sliding window
• How array rotation works internally
• Importance of avoiding duplicate values
• Thinking in step-by-step logic

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🔥 Key Takeaway

Most problems are just:

loop + condition + array manipulation

Once that pattern clicks, everything becomes easier.

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💬 Note

Still learning, still improving.

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