View Compilation Error

0_0_30379025_13995.c:2:8: error: variably modified 'p' at file scope
 double p[maxn];
        ^
0_0_30379025_13995.c: In function 'main':
0_0_30379025_13995.c:6:5: error: 'cin' undeclared (first use in this function)
     cin >> T;
     ^
0_0_30379025_13995.c:6:5: note: each undeclared identifier is reported only once for each function it appears in
0_0_30379025_13995.c:9:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
         for (int i = 1; i <= n; ++i) {
         ^
0_0_30379025_13995.c:9:9: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_30379025_13995.c:18:13: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
             for (int i = n; i >= 1; --i) {
             ^