阿木博主一句话概括：PL/I语言中图的遍历算法实现：深度优先与广度优先
阿木博主为你简单介绍：
图是数据结构中的一种，广泛应用于计算机科学和实际应用中。图的遍历是图论中的一个基本问题，它指的是访问图中所有顶点的过程。在PL/I语言中，我们可以通过编写程序来实现图的深度优先遍历（DFS）和广度优先遍历（BFS）。本文将详细介绍这两种遍历算法在PL/I语言中的实现方法，并分析其优缺点。
一、
图的遍历是图论中的一个重要概念，它涉及到如何访问图中的所有顶点。在图论中，图的遍历主要有两种方法：深度优先遍历（DFS）和广度优先遍历（BFS）。本文将分别介绍这两种遍历算法在PL/I语言中的实现。
二、深度优先遍历（DFS）
深度优先遍历是一种非线性的遍历方法，它从某个顶点开始，沿着一条路径一直走到尽头，然后再回溯，继续沿着另一条路径进行遍历。以下是DFS在PL/I语言中的实现代码：
pl/i
IDENTIFICATION DIVISION.
PROGRAM-ID. DFS-Traversal.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT OUTPUT-FILE ASSIGN TO "output.txt".
DATA DIVISION.
FILE SECTION.
FD OUTPUT-FILE.
01 OUTPUT-REC PIC X(100).
WORKING-STORAGE SECTION.
01 VERTICES PIC 9(2) VALUE 5.
01 ADJACENCY-MATRIX PIC 9(2) OCCURS 5 TIMES.
01 VISITED PIC X(1) OCCURS 5 TIMES VALUE SPACES.
01 CURRENT-VERTEX PIC 9(2) VALUE 1.
01 STACK PIC 9(2) OCCURS 5 TIMES.
01 STACK-POINTER PIC 9(2) VALUE 0.
PROCEDURE DIVISION.
PERFORM INITIALIZE-GRAPH.
PERFORM DFS-TRAVEL.
PERFORM PRINT-TRAVEL.
STOP RUN.
INITIALIZE-GRAPH.
MOVE 1 TO ADJACENCY-MATRIX(1,1).
MOVE 1 TO ADJACENCY-MATRIX(1,2).
MOVE 1 TO ADJACENCY-MATRIX(2,1).
MOVE 1 TO ADJACENCY-MATRIX(2,2).
MOVE 1 TO ADJACENCY-MATRIX(2,3).
MOVE 1 TO ADJACENCY-MATRIX(3,2).
MOVE 1 TO ADJACENCY-MATRIX(3,3).
MOVE 1 TO ADJACENCY-MATRIX(3,4).
MOVE 1 TO ADJACENCY-MATRIX(4,3).
MOVE 1 TO ADJACENCY-MATRIX(4,4).
DFS-TRAVEL.
PERFORM VERTICES-UNVISITED.
PERFORM VISIT-VERTEX.
PERFORM DFS-RECURSIVE.
VERTICES-UNVISITED.
IF CURRENT-VERTEX > VERTICES THEN
EXIT PERFORM
END-IF.
VISIT-VERTEX.
IF VISITED(CURRENT-VERTEX) = 'N' THEN
MOVE CURRENT-VERTEX TO STACK(STACK-POINTER)
ADD 1 TO STACK-POINTER
MOVE 'Y' TO VISITED(CURRENT-VERTEX)
PERFORM PRINT-VERTEX
END-IF.
DFS-RECURSIVE.
PERFORM NEXT-VERTEX.
PERFORM DFS-TRAVEL.
NEXT-VERTEX.
IF STACK-POINTER > 0 THEN
SUBTRACT 1 FROM STACK-POINTER
MOVE STACK(STACK-POINTER) TO CURRENT-VERTEX
ELSE
EXIT PERFORM
END-IF.
PRINT-VERTEX.
MOVE CURRENT-VERTEX TO OUTPUT-REC
WRITE OUTPUT-REC ON OUTPUT-FILE.
PRINT-TRAVEL.
OPEN OUTPUT OUTPUT-FILE.
READ OUTPUT-FILE.
CLOSE OUTPUT-FILE.
三、广度优先遍历（BFS）
广度优先遍历是一种线性的遍历方法，它从某个顶点开始，访问其所有相邻的顶点，然后再访问这些顶点的相邻顶点，以此类推。以下是BFS在PL/I语言中的实现代码：
pl/i
IDENTIFICATION DIVISION.
PROGRAM-ID. BFS-Traversal.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT OUTPUT-FILE ASSIGN TO "output.txt".
DATA DIVISION.
FILE SECTION.
FD OUTPUT-FILE.
01 OUTPUT-REC PIC X(100).
WORKING-STORAGE SECTION.
01 VERTICES PIC 9(2) VALUE 5.
01 ADJACENCY-MATRIX PIC 9(2) OCCURS 5 TIMES.
01 VISITED PIC X(1) OCCURS 5 TIMES VALUE SPACES.
01 CURRENT-VERTEX PIC 9(2) VALUE 1.
01 QUEUE PIC 9(2) OCCURS 5 TIMES.
01 FRONT PIC 9(2) VALUE 1.
01 REAR PIC 9(2) VALUE 1.
PROCEDURE DIVISION.
PERFORM INITIALIZE-GRAPH.
PERFORM BFS-TRAVEL.
PERFORM PRINT-TRAVEL.
STOP RUN.
INITIALIZE-GRAPH.
-- (Same as DFS-Traversal)
BFS-TRAVEL.
PERFORM VERTICES-UNVISITED.
PERFORM VISIT-VERTEX.
PERFORM BFS-RECURSIVE.
VERTICES-UNVISITED.
-- (Same as DFS-Traversal)
VISIT-VERTEX.
IF VISITED(CURRENT-VERTEX) = 'N' THEN
MOVE CURRENT-VERTEX TO QUEUE(REAR)
ADD 1 TO REAR
MOVE 'Y' TO VISITED(CURRENT-VERTEX)
PERFORM PRINT-VERTEX
END-IF.
BFS-RECURSIVE.
PERFORM NEXT-VERTEX.
PERFORM BFS-TRAVEL.
NEXT-VERTEX.
IF FRONT <= REAR THEN
SUBTRACT 1 FROM REAR
MOVE QUEUE(FRONT) TO CURRENT-VERTEX
ADD 1 TO FRONT
ELSE
EXIT PERFORM
END-IF.
PRINT-VERTEX.
-- (Same as DFS-Traversal)
PRINT-TRAVEL.
-- (Same as DFS-Traversal)
四、总结
本文介绍了在PL/I语言中实现图的深度优先遍历（DFS）和广度优先遍历（BFS）的方法。通过编写程序，我们可以访问图中的所有顶点，并了解两种遍历算法的特点。在实际应用中，根据具体需求选择合适的遍历算法，可以提高程序的效率和性能。
需要注意的是，本文提供的代码仅为示例，实际应用中可能需要根据具体情况进行调整。PL/I语言在现代社会中已较少使用，但了解其基本语法和编程思想对于学习其他编程语言仍然具有一定的参考价值。
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