diff --git a/sudoku4.c b/sudoku4.c
new file mode 100644
index 0000000..35624a1
--- /dev/null
+++ b/sudoku4.c
@@ -0,0 +1,178 @@
+/*-------------------*/
+/*实验：数独矩阵------*/
+/*4. 对一个不完整的“数独矩阵”进行判断，如果满足“数独矩阵”则补充完整，*/
+/*使之成为一个完整的“数独矩阵”：*/
+/*-------------------*/
+#include<stdio.h>
+#include<stdlib.h>
+#include<time.h>
+void randseedInit(){
+    srand(time(NULL));
+}
+void printBoad(int _board[9][9]){
+	int i,j; 
+    for ( i = 0; i < 9;i++){
+        if(!(i%3))printf("|-----------------------|\n");
+        for ( j = 0; j < 9;j++){
+            if(!(j%3))
+                printf("| ");
+            if(_board[i][j]==0)
+                printf(". ");
+            else 
+                printf("%d ", _board[i][j]);
+        }
+        printf("|\n");
+    }
+    printf("|-----------------------|\n");
+}
+void makeNSeq(int _seq[],int n){//产生1-n的不重复序列（传入一个数组名指针）
+    int ct[9] = {0, 0, 0, 0, 0, 0, 0, 0, 0};
+    int i;
+    for (i = 0; i < n; i++) {
+        int t = rand() % n;
+        while(ct[t=rand() % n]);
+        ct[t]++;
+        _seq[i] = t+1;
+    }
+}
+void initBoard(int _board[9][9]){
+	int i,j;
+    for ( i = 0; i < 9;i++)
+        for ( j = 0; j < 9;j++)
+            _board[i][j] = 0;
+}
+void makeRandomBoard(int _board[9][9]){
+    initBoard(_board);
+    int i_1,i,idx;
+    for ( i_1 = 0; i_1 < 3;i_1++){
+        int seq[9];
+        makeNSeq(seq, 9);
+        for ( i = 0; i < 3;i++){
+            int where[9];
+            makeNSeq(where, 9);
+            for ( idx = 0; idx < 3;idx++){
+                _board[i_1 * 3 + i][where[idx+i*3]-1] = seq[idx+i*3];
+            }
+        }
+    }
+}
+void printWhyInvalid(int num,int is_col,int index,int *valid,int ndpt){
+    if(*valid){
+        if(ndpt)printf("False:Invalid initial Sudoku matrix!\n      The number %d in the %s %d has been used!\n", num, (is_col ? "col" : "block"), index);
+        *valid = 0;
+    };
+}
+int whoBeUsedInSeq(int seq[9]){
+    int ct[10]={0,0,0,0,0,0,0,0,0,0};
+    int i;
+    for ( i = 0; i < 9;i++){
+        ct[seq[i]]++;
+    }
+    for (i = 1; i < 10;i++){
+        if(ct[i]>1)
+            return i;
+    }
+    return 0;
+}
+void matrixT(int _board[9][9],int _output[9][9]){
+	int i,j;
+    for (i = 0; i < 9;i++)
+        for ( j = 0; j < 9;j++)
+            _output[j][i] = _board[i][j];
+}
+void resortByBlock(int _board[9][9], int _output[9][9]) {
+	int i,j;
+    for ( i = 0; i < 9;i++){
+        int p1x = i / 3;
+        int p1y = i % 3;
+        for (j = 0; j < 9; j++){
+            int p2x = j / 3;
+            int p2y = j % 3;
+            _output[i][j] = _board[p1x * 3 + p2x][p1y * 3 + p2y];
+        }
+    }
+}
+int judgeValid(int _board[9][9],int ndpt){
+    int valid = 1;
+    int boardT[9][9];
+    int boardB[9][9];
+    matrixT(_board, boardT);
+    resortByBlock(_board, boardB);
+    int i;
+    for ( i = 0; i < 9;i++){
+        int who = whoBeUsedInSeq(boardT[i]);
+        if(who)
+            printWhyInvalid(who, 1, i+1, &valid,ndpt);
+        who = whoBeUsedInSeq(boardB[i]);
+        if(who)
+            printWhyInvalid(who, 0, i+1, &valid,ndpt);
+        who = whoBeUsedInSeq(_board[i]);
+        if(who)
+            valid = 0;
+    }
+    return valid;
+}
+int try(int _b[9][9],int where[]){
+    int w = where[0];
+    if(!judgeValid(_b,0))
+        return 0;
+    if(w==-1){
+        printf("The Solution of Sudoku Matrix:\n");
+        printBoad(_b);
+        return 1;
+    }
+    int n,i,j;
+    for ( n = 1; n <= 9;n++){
+        int _bt[9][9];
+        for ( i = 0; i < 9;i++)
+            for ( j = 0; j < 9;j++)
+                _bt[i][j] = _b[i][j];
+        _bt[w / 9][w % 9] = n;
+        if(try(_bt, &where[1])){
+            return 1;
+        }
+    }
+    return 0;
+}
+int solve(int _board[9][9]){
+    int idx = 0;
+    int where[81];
+    int _b[9][9];
+    int i,j;
+    for ( i = 0; i < 9;i++)
+        for ( j = 0; j < 9;j++)
+            _b[i][j] = _board[i][j];
+    for ( i = 0; i < 81;i++)
+        where[i] = -3;
+    int pos = 0;
+    while (pos < 81) {
+        if (!_b[pos / 9][pos % 9]){
+            where[idx]=pos;
+            idx++;
+        }
+        pos++;
+    }
+    where[idx] = -1;
+    if(try(_b, where)){
+        
+        return 1;
+    }
+    else{
+        printf("No Solution!\n");
+         return 0;
+    };
+}
+int main(){
+    randseedInit();
+    int board[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}};
+    printBoad(board);
+    solve(board);
+}