answer.code: In function ‘findIndex’:
answer.code:4:5: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
    4 |     for (int i = 1; i < size; i++) {
      |     ^~~
answer.code:4:5: note: use option ‘-std=c99’, ‘-std=gnu99’, ‘-std=c11’ or ‘-std=gnu11’ to compile your code
answer.code:7:24: error: C++ style comments are not allowed in ISO C90
    7 |             return i;  // ????????????
      |                        ^
answer.code:7:24: note: (this will be reported only once per input file)
answer.code: In function ‘main’:
answer.code:38:5: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
   38 |     for(int i=1;i<=n;i++){
      |     ^~~
answer.code:43:9: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
   43 |         for(int i=1;i<n+1-i;i++,j++){
      |         ^~~
answer.code:48:9: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
   48 |         for(int i=1;i<=n+1-i;i++,k++){
      |         ^~~
answer.code:52:15: error: redefinition of ‘i’
   52 |       for(int i=0;i<j;i++){
      |               ^
answer.code:38:13: note: previous definition of ‘i’ was here
   38 |     for(int i=1;i<=n;i++){
      |             ^
answer.code:52:7: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
   52 |       for(int i=0;i<j;i++){
      |       ^~~
answer.code:61:13: error: redefinition of ‘i’
   61 |     for(int i=0;i<k;i++){
      |             ^
answer.code:52:15: note: previous definition of ‘i’ was here
   52 |       for(int i=0;i<j;i++){
      |               ^
answer.code:61:5: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
   61 |     for(int i=0;i<k;i++){
      |     ^~~
answer.code:71:9: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
   71 |         for(int c=1,b=0;c<n+1;c++,b++){
      |         ^~~
answer.code:76:9: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
   76 |         for(int c=1,b=0;c<n+1;c++,b++){
      |         ^~~
answer.code:80:13: error: redefinition of ‘i’
   80 |     for(int i=0;i<n;i++){
      |             ^
answer.code:61:13: note: previous definition of ‘i’ was here
   61 |     for(int i=0;i<k;i++){
      |             ^
answer.code:80:5: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
   80 |     for(int i=0;i<n;i++){
      |     ^~~
answer.code:29:5: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result]
   29 |     scanf("%d",&n);
      |     ^~~~~~~~~~~~~~
answer.code:39:9: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result]
   39 |         scanf("%d",&ar_1[i]);
      |         ^~~~~~~~~~~~~~~~~~~~