diff --git a/README.md b/README.md
index 3d8a8fb..db73b1e 100644
--- a/README.md
+++ b/README.md
@@ -32,4 +32,175 @@ for(i=0;i<9;i++)
     }
 }
 }
+数独实验第3题
+#include<stdio.h>
+int main()
+{
+int board0[9][9] = { {5, 3, 0, 0, 7, 0, 0, 0, 0},
+{6, 0, 0, 1, 9, 5, 0, 0, 0},
+{0, 9, 8, 0, 0, 0, 0, 6, 0},
+{8, 0, 0, 0, 6, 0, 0, 0, 3},
+{4, 0, 0, 8, 0, 3, 0, 0, 1},
+{7, 0, 0, 0, 2, 0, 0, 0, 6},
+{0, 6, 0, 0, 0, 0, 2, 8, 0},
+{0, 0, 0, 4, 1, 9, 0, 0, 5},
+{0, 0, 0, 0, 8, 0, 0, 7, 9} };
+int i, j,x,y,m=0;
+printf("The original Sudoku matrix:\n ");
+for (i = 0; i < 9; i++)
+{
+for (j = 0; j < 9; j++)
+{
+printf("%-2d", board0[i][j]);
+if (j == 8)
+{
+printf("\n");
+}
+}
+}
+for (i = 0; i < 9; i++)
+{
+for (j = 0; j < 9; j++)
+{
+if (board0[i][j] != 0)
+{
+x = i + 1;
+y = j + 1;
+for (; y < 9;y++)
+{
+if (board0[i][j] != board0[i][y])
+{
+m = m;
+}
+else
+{
+m++;
+}
+}
+for (; x < 9; x++)
+{
+if (board0[i][j] != board0[x][j])
+{
+m = m;
+}
+else
+{
+m++;
+}
+}
 
+}
+else
+{
+continue;
+}
+}
+}
+if (m == 0)
+{
+printf("True:Valid initial Sudoku matrix!\n");
+}
+else
+{
+printf("False:Invalid initial Sudoku matrix!\n");
+}
+}
+数独实验第4题（部分）
+#include <stdio.h>
+#include <stdlib.h>
+#define N 3 
+#define M 9 
+#include<stdio.h>
+int x[M][M]={{8, 3, 0, 0, 7, 0, 0, 0, 0},
+                   {6, 0, 0, 1, 9, 5, 0, 0, 0},
+                   {0, 9, 8, 0, 0, 0, 0, 6, 0},
+                   {8, 0, 0, 0, 6, 0, 0, 0, 3},
+                   {4, 0, 0, 8, 0, 3, 0, 0, 1},
+                   {7, 0, 0, 0, 2, 0, 0, 0, 6},
+                   {0, 6, 0, 0, 0, 0, 2, 8, 0},
+                   {0, 0, 0, 4, 1, 9, 0, 0, 5},
+                   {0, 0, 0, 0, 8, 0, 0, 7, 9}};
+void Solve(int r, int c);  
+int checkedbox(int r);
+int checked(int r, int c, int num);
+int* getData(int r, int c,int *data);
+void show(void);  
+void Solve(int r, int c) 
+{
+int i;
+if (r == M) {
+show();
+return; 
+}
+if (c == 0 && (r == N || r == N*2)) {
+if (checkedbox(r) == 0) { 
+return; 
+}
+}
+if (c == M) {
+Solve(r+1, 0);
+return;
+}
+if (x[r][c] == 0) { 
+for (i = 1; i <= M; i++) { 
+if (checked(r,c,i) == 1) {
+x[r][c]=i;
+Solve(r, c+1);
+x[r][c]=0;
+}
+}
+}
+else{
+Solve(r, c+1);
+}
+}
+int checkedbox(int r) {
+  int i,j,c;
+  int *data = malloc(sizeof(int)*M);
+for (c = 0; c < M; c+=N) { 
+data = getData(r,c,data); 
+for(i = 0; i < M-1 ; i++) {
+for(j = i+1 ; j < M ; j++) {
+if(data[i] == data[j]) { 
+return 0; 
+}
+}
+}
+}
+free(data); 
+return 1;  
+}
+int* getData(int r, int c,int *data){
+int i,j,k = 0;
+for (i = r-N; i < r ; i++) { 
+for(j = c; j < c+N ; j++){
+data[k++] = x[i][j];
+}
+}
+return data; 
+}
+int checked(int r, int c, int num) {
+int j = 0,flag = 1;
+for (j = 0; j < M; j++) {
+if (x[j][c]==num || x[r][j]==num) {
+flag = 0;
+}
+}
+return flag;
+}
+void show(void) {
+int i,j;
+for (i = 0; i < M; i++) {
+for (j = 0; j < M; j++) {
+printf("%d ",x[i][j]);
+}
+printf("\n");
+}
+printf("\n");
+}
+ 
+int main(void)
+{
+Solve(0,0);
+return 0;
+}
\ No newline at end of file