题解 | 上三角矩阵判定

import java.util.Scanner

fun main(args: Array<String>){
    val reader = Scanner(System.`in`)
    //读取第一行的整数n
    val n = reader.nextLine().trim().toInt()
    //创建二维数组存储矩阵
    val matrix = Array(n,{ IntArray(n) })
    for (i in 0 until n) {
        val rowInput = reader.nextLine().split(" ").map { it.toInt() }
        if (rowInput.size != null && rowInput.size>=n){
            for(j in rowInput.indices){
                matrix[i][j] = rowInput[j]
            }
        }
    }
    var isUpTriangle = true
    for (i in 0 until n){
        for (j in 0 until i){
            if (matrix[i][j]!=0){
                isUpTriangle = false
            }
        }
    }
    if (isUpTriangle) {
        println("YES")
    }else{
        println("NO")
    }
}