View Compilation Error

0_0_13273854_21132.c: In function 'main':
0_0_13273854_21132.c:23:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
         for(int i=0;i<len;i++)
         ^
0_0_13273854_21132.c:23:9: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_13273854_21132.c:42:17: error: redefinition of 'i'
         for(int i=0;i<=len2;i++)
                 ^
0_0_13273854_21132.c:23:17: note: previous definition of 'i' was here
         for(int i=0;i<len;i++)
                 ^
0_0_13273854_21132.c:42:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
         for(int i=0;i<=len2;i++)
         ^
0_0_13273854_21132.c:48:17: error: redefinition of 'i'
         for(int i=1;i<=len2;i++)
                 ^
0_0_13273854_21132.c:42:17: note: previous definition of 'i' was here
         for(int i=0;i<=len2;i++)
                 ^
0_0_13273854_21132.c:48:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
         for(int i=1;i<=len2;i++)
         ^