Good day to you!

Well because "temp" might not be initialized when you use it:

if(i != j && j != k && i != k){
    temp = num[i] + let[j] + sym[k];
}
if(temp < INF){
    ans = min(ans, temp);
}

If the first condition is not "OK" and temp was not set yet, it could bring in an undefined value (such as -INF).

Setting it to INF shall get you AC.

But no clue whether the change of inf can influence it somehow (but as you can see, those INF's are different numbers, so perhaps something "in your code" [first inf is 10^10 second just 10^9] )

Good Luck & Have Nice Day.

10e9 is actually 10¹⁰. Try defining INF as 1e9.

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