无序: 排序以外的奇淫技巧

static int findMissingNumber(int start, int end, List<Integer> list) {
    int sum=0;    
    int count=0;    
    for(Integer i:list){
        sum=i+sum;    
    }
    for(int i=start;i<=end;i++){
        count=count+i;    
    }
    return count-sum;
}