剑指Offer（十九）：顺时针打印矩阵
一、前言
本系列文章为《剑指Offer》刷题笔记。
刷题平台：牛客网
书籍下载：共享资源
二、题目
输入一个矩阵，按照从外向里以顺时针的顺序依次打印出每一个数字，例如，如果输入如下矩阵：
则依次打印出数组：1，2，3，4，8，12，16，15，14，13，9，5，6，7，11，10。
1、思路
将结果存入vector数组，从左到右，再从上到下，再从右到左，最后从下到上遍历。
2、代码
C++：
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class Solution {
public:
vector<int> printMatrix(vector<vector<int> > matrix) {
int rows = matrix.size(); //行数
int cols = matrix[0].size(); //列数
vector<int> result;
if(rows == 0 && cols == 0){
return result;
}
int left = 0, right = cols - 1, top = 0, bottom = rows - 1;
while(left <= right && top <= bottom){
//从左到右
for(int i = left; i <= right; ++i){
result.push_back(matrix[top][i]);
}
//从上到下
for(int i = top + 1; i <= bottom; ++i){
result.push_back(matrix[i][right]);
}
//从右到左
if(top != bottom){
for(int i = right - 1; i >= left; --i){
result.push_back(matrix[bottom][i]);
}
}
//从下到上
if(left != right){
for(int i = bottom - 1; i > top; --i){
result.push_back(matrix[i][left]);
}
}
left++, top++, right--, bottom--;
}
return result;
}
};
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Python2.7：
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# -*- coding:utf-8 -*-
class Solution:
# matrix类型为二维列表，需要返回列表
def printMatrix(self, matrix):
# write code here
rows = len(matrix)
cols = len(matrix[0])
result = []
if rows == 0 and cols == 0:
return result
left, right, top, buttom = 0, cols - 1, 0, rows - 1
while left <= right and top <= buttom:
for i in range(left, right+1):
result.append(matrix[top][i])
for i in range(top+1, buttom+1):
result.append(matrix[i][right])
if top != buttom:
for i in range(left, right)[::-1]:
result.append(matrix[buttom][i])
if left != right:
for i in range(top+1, buttom)[::-1]:
result.append(matrix[i][left])
left += 1
top += 1
right -= 1
buttom -= 1
return result
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题目变型：
给定一个数字2，打印矩阵：
给定一个数字3，打印矩阵：
给定一个数字4，打印矩阵：
Python：
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# -*- coding:utf-8 -*-
def matrix(target):
num = target * target
left, right, top, bottom = 0, target-1, 0, target-1
res = [ [0 for col in range(target)] for row in range(target)]
each = 1
while left <= right and top <= bottom and each <= num:
for i in range(left, right+1):
res[top][i] = each
each += 1
for i in range(top+1, bottom+1):
res[i][right] = each
each += 1
if top != bottom:
for i in range(left, right)[::-1]:
res[bottom][i] = each
each += 1
if left != right and each <= num:
for i in range(top+1, bottom)[::-1]:
res[i][left] = each
each += 1
top += 1
left += 1
bottom -= 1
right -= 1
for i in range(len(res)):
print("\t".join('%s' %id for id in res[i]))
if __name__ == '__main__':
matrix(4)
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