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Find missing number in 1..n — sum formula vs XOR approach.
FresherFundamentalsData Structures & Algorithms
Missing 1..n
java
int missing(int[] nums) {
int n = nums.length;
int sum = n * (n + 1) / 2;
for (int x : nums) sum -= x;
return sum;
}Sum formula O(n); XOR alternative avoids overflow concerns in theory.
Watch overflow for large n—use long or XOR.