Driver function
public static void Main ( ) { int [ , ] mat = { { 1 , 3 , 5 , 3 } , { 0 , 4 , 6 , 2 } , { 0 , 0 , 2 , 5 } , { 0 , 0 , 0 , 6 } } ; if ( isUpperTriangularMatrix ( mat ) ) Console . WriteLine ( " Yes " ) ; else Console . WriteLine ( " No " ) ; } }