Objective C solution to https://leetcode.com/problems/count-and-say/description/

CountAndCall.m

#import <Foundation/Foundation.h>

@interface Solution : NSObject
- (NSString *)countAndCall: (int) n;
- (NSString *)count:(int) n;
@end

@implementation Solution

- (NSString *)countAndCall: (int) n {
    
    return [self count:n];
}

- (NSString *)count:(int) n {
    if(n<=1) return @"1";
    
    NSString *s=[self count:n-1];
    NSMutableString *res=[[NSMutableString alloc] initWithString:@""];
    int cnt=1;
    
    for(int i=0; i<s.length; i++) {
        char c1=[s characterAtIndex:i];
        if(i==s.length-1 || c1 != [s characterAtIndex:i+1]) {
            [res appendString:[NSString stringWithFormat:@"%d",cnt]];
            [res appendString:[NSString stringWithFormat:@"%c",c1]];
            
            cnt=1;
        }
        else {
            cnt++;
        }
    }
    return res;
}

@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        int cont;
        do {
            int n;
            printf("Number: ");
            scanf("%d", &n);
            printf("\n");
            Solution *sol=[[Solution alloc] init];
            printf("%s\n",[[sol countAndCall:n] UTF8String]);
            scanf("%d",&cont);
        } while (cont!=0);
    }
    return 0;
}