LeetCode_268-Missing Number

Solution:

思路：利用有序性以及求和思想求出期待的和值，减去当前值即可得出缺失值

int missingNumber(vector<int>& nums) {

int sum = 0;

int desired_sum = (1 + nums.size()) * nums.size() / 2;

for(vector<int>::iterator a = nums.begin(); a!=nums.end();a++){

sum += *a;

}

return ((sum==desired_sum) ? 0 : desired_sum - sum);

}