diff --git a/数独矩阵第四关.c b/数独矩阵第四关.c
new file mode 100644
index 0000000..91673fd
--- /dev/null
+++ b/数独矩阵第四关.c
@@ -0,0 +1,204 @@
+#include <stdio.h>
+
+void print_valid(int a[9][9]){
+	int x=1;
+	int i,j,ii,jj;
+	for (i = 0; i < 9; i++) {
+		int count[10] = {0};
+		for (j = 0; j < 9; j++) {
+			if (a[i][j]!= 0) {
+				if (count[a[i][j]] > 0) {
+					x = 0;
+					printf("False:Invalid initial Sudoku matrix!\n      The number %d in the row %d has been used!\n", a[i][j], i + 1);
+					return;
+				}
+				count[a[i][j]]++;
+			}
+		}
+	}
+	int y=1;
+	for (j = 0; j < 9; j++) {
+		int count[10] = {0};
+		for (i = 0; i <9; i++) {
+			if (a[i][j]!= 0) {
+				if (count[a[i][j]] > 0) {
+					y = 0;
+					printf("False:Invalid initial Sudoku matrix!\n      The number %d in the col %d has been used!\n", a[i][j], j + 1);
+					return;
+				}
+				count[a[i][j]]++;
+			}
+		}
+	}
+	int z=1;
+	for (i = 0; i <9; i += 3) {
+		for (j = 0; j <9; j += 3) {
+			int count[10] = {0};
+			for (ii = i; ii < i + 3; ii++) {
+				for (jj = j; jj < j + 3; jj++) {
+					if (a[ii][jj]!= 0) {
+						if (count[a[ii][jj]] > 0) {
+							z = 0;
+							printf("False:Invalid initial Sudoku matrix!\n      The number %d in the 3x3 submatrix starting at row %d, col %d has been used!\n", a[ii][jj], i + 1, j + 1);
+							return;
+						}
+						count[a[ii][jj]]++;
+					}
+				}
+			}
+		}
+	}
+	if (x&&y&&z) {
+	printf("True:Valid initial Sudoku matrix!\n");
+	}
+	return;
+}
+
+int is_valid(int a[9][9]){
+	int x=1;
+	int i,j,ii,jj;
+	for (i = 0; i < 9; i++) {
+		int count[10] = {0};
+		for (j = 0; j < 9; j++) {
+			if (a[i][j]!= 0) {
+				if (count[a[i][j]] > 0) {
+					x = 0;
+					return 0;
+				}
+				count[a[i][j]]++;
+			}
+		}
+	}
+	int y=1;
+	for (j = 0; j < 9; j++) {
+		int count[10] = {0};
+		for (i = 0; i <9; i++) {
+			if (a[i][j]!= 0) {
+				if (count[a[i][j]] > 0) {
+					y = 0;
+					return 0;
+				}
+				count[a[i][j]]++;
+			}
+		}
+	}
+	int z=1;
+	for (i = 0; i <9; i += 3) {
+		for (j = 0; j <9; j += 3) {
+			int count[10] = {0};
+			for (ii = i; ii < i + 3; ii++) {
+				for (jj = j; jj < j + 3; jj++) {
+					if (a[ii][jj]!= 0) {
+						if (count[a[ii][jj]] > 0) {
+							z = 0;
+							return 0;
+						}
+						count[a[ii][jj]]++;
+					}
+				}
+			}
+		}
+	}
+	if (x&&y&&z) {
+	}
+	return 1;
+}
+
+int solve_sudoku(int a[9][9]) {
+	int row,col,num;
+    for (row = 0; row < 9; row++) {
+        for (col = 0; col < 9; col++) {
+            if (a[row][col] == 0) {
+                for (num = 1; num <= 9; num++) {
+                    if (is_valid(a)) {
+                        a[row][col] = num;
+                        if (solve_sudoku(a)) {
+                            return 1;
+                        }
+                        a[row][col] = 0;
+                    }
+                }
+                return 0;
+            }
+        }
+    }
+    return 1;
+}
+
+void print(int a[9][9]) {
+	printf("|-----------------------|\n");
+    int i,j;
+	for(i=0;i<9;i++){
+		printf("| ");
+		for(j=0;j<9;j++){
+			printf("%d ",a[i][j]);
+			if(j==2||j==5) printf("| ");
+			if(j==8) printf("|\n");
+		}
+		if(i==2||i==5) {
+			int x=22;
+			printf("|");
+			while(x>=0) {
+				printf("-");
+				x--;
+			}
+			printf("|\n");
+		}
+	}
+	printf("|-----------------------|\n");
+}
+
+void final(int a[9][9]) {
+    printf("The original Sudoku matrix: \n");
+    print(a);
+    int valid=is_valid(a);
+    print_valid(a);
+    if(valid){
+    	if (solve_sudoku(a)) {
+            printf("The solution of Sudoku matrix:\n");
+            print(a);
+		}
+		else printf("No solution!\n");
+	}
+	else printf("No solution!\n");
+}
+
+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}
+	};
+	final(board0);
+	int board1[9][9] = {
+	{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}
+	};
+	final(board1);
+	int board2[9][9] = {
+	{5, 2, 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}
+	};
+	final(board2);
+	return 0;
+}