public class Solution {
public int findDuplicate(int[] nums) {
int start = 1, end = nums.length - 1, mid;
while (start < end) {
mid = start + (end - start) / 2;
int count = 0;
for (int num : nums) {
if (num <= mid) count++;
}
if (count > mid) {
end = mid;
} else {
start = mid + 1;
}
}
return start;
}
}