Add a new column to problem model

@@ -8,6 +8,7 @@ const ProblemSchema=new Schema({
     solvedacLevel: {type: Number},
     sumbitNum: {type: Number, required: true},
     correctNum: {type: Number, required: true},
+    count: { type: Number },
     category: {type:[String]}
 });
 
@@ -46,6 +47,10 @@ ProblemSchema.methods.getCorrectNum=function(){
     return this.correctNum;
 }
 
+ProblemSchema.methods.getCount=function(){
+    return this.count;
+}
+
 ProblemSchema.methods.getCategory=function(){
     return this.category;
 }