答案

#include <stdio.h>

int main(int argc, const char * argv[]) {
    
    int kLineCount = 30;

    for (int i = 0; i < kLineCount; i++) {
        
        for (int j = 0; j < kLineCount - i; j++) {
            printf(" ");
        }
        
        for (int j = 0; j < 2 * i + 1; j++) {
            printf("*");
        }
        printf("\n");
    }
    
    for (int i = kLineCount; i > 0; i--) {
        
        for (int j = kLineCount; j > 0 + i; j--) {
            printf(" ");
        }
        
        for (int j = 2 * i - 1; j > 0; j--) {
            printf("*");
        }
        printf("\n");
    }
    return 0;
}