foo.cc: In function 'void MergeSort_(int, int)':
foo.cc:14:49: warning: operation on 'i' may be undefined [-Wsequence-point]
14 | if(a[i+1]>=b[j+1]) num[i+j+l]=a[++i];
| ^~~
foo.cc:14:49: warning: operation on 'i' may be undefined [-Wsequence-point]
foo.cc:15:35: warning: operation on 'j' may be undefined [-Wsequence-point]
15 | else num[i+j+l]=b[++j];
| ^~~
foo.cc:15:35: warning: operation on 'j' may be undefined [-Wsequence-point]
foo.cc:17:35: warning: operation on 'i' may be undefined [-Wsequence-point]
17 | while(i!=la) num[i+j+l]=a[++i]; //b数组填完了 轮到a数组了
| ^~~
foo.cc:17:35: warning: operation on 'i' may be undefined [-Wsequence-point]
foo.cc:18:35: warning: operation on 'j' may be undefined [-Wsequence-point]
18 | while(j!=lb) num[i+j+l]=b[++j]; //a数组填完了 轮到b数组了
| ^~~
foo.cc:18:35: warning: operation on 'j' may be undefined [-Wsequence-point]
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