foo.cc: In function 'int main()':
foo.cc:10:6: warning: iteration 9 invokes undefined behavior [-Waggressive-loop-optimizations]
 a[i] = i;
 ~~~~~^~~
foo.cc:8:12: note: within this loop
 for (i=1; i<=10; i++) //为三个数组赋值1-9
           ~^~~~

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