https://leetcode.com/problems/reverse-integer/
class Solution { public: int inf = ~0u >> 1; int reverse(int x) { if(x == 0)return 0; long long tx = x; long long ans = 0; for(int i = 0;tx;i++){ ans = ans * 10 + tx % 10; tx /= 10; } return int(ans) == ans?ans:0; } };