diff --git a/4th.c b/4th.c
new file mode 100644
index 0000000..659c826
--- /dev/null
+++ b/4th.c
@@ -0,0 +1,75 @@
+#include<stdio.h>
+#include<stdlib.h>
+typedef struct {
+	int ID;
+	int classnumber;
+	float score1,score2,score3;
+}student;
+
+void insert(student students[],int *n,student new){
+	int k=0;
+	int j=*n-1;
+	for( k;k<=*n;k++){
+		if(k==*n||students[k].classnumber>new.classnumber){
+			for( j;j>=k;j--){
+				students[j+1]=students[j];
+			}
+			students[k]= new;
+			(*n)++;
+			break;
+		}else if(students[k].ID==new.ID){
+			printf("已存在学号的信息\n");
+			return;
+		}
+	}
+}
+int compare(const void*a,const void *b){
+	student s1=*(student*)a;
+	student s2=*(student*)b;
+	if(s1.classnumber!=s2.classnumber){
+		return s1.classnumber-s2.classnumber;
+	}
+	float total1=s1.score1+s1.score2+s1.score3;
+	float total2=s2.score1+s2.score2+s2.score3;
+	return total2-total1;
+}
+int main(){
+	int n=3;
+	student students[5]={
+	{10001,11,99.5,88.5,89.5},
+	{10002,12,77.9,56.5,87.5},
+	{10003,11,92.5,99.0,60.5}};
+	student new;
+	scanf("%d %d %f %f %f", &new.ID, &new.classnumber,&new.score1, &new.score2, &new.score3);
+	insert(students,&n,new);
+	qsort(students,n,sizeof(student),compare);
+	int i=0;
+	for( i;i<n;i++){
+		printf("%d %d %.1f %.1f %.1f",students[i].ID,students[i].classnumber,students[i].score1,students[i].score2,students[i].score3);
+		if(students[i].ID==new.ID){
+			printf(" inserted\n");
+		}else{
+			printf("\n");
+		}
+	}
+	return 0;
+}
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