标签：规划 class exp 问题 span return ber ++ size
问题：
给定由0，1构成的数组，求由1构成的（各种长度边长的）正方形的总个数有多少。
Example 1: Input: matrix = [ [0,1,1,1], [1,1,1,1], [0,1,1,1] ] Output: 15 Explanation: There are 10 squares of side 1. There are 4 squares of side 2. There is 1 square of side 3. Total number of squares = 10 + 4 + 1 = 15. Example 2: Input: matrix = [ [1,0,1], [1,1,0], [1,1,0] ] Output: 7 Explanation: There are 6 squares of side 1. There is 1 square of side 2. Total number of squares = 6 + 1 = 7. Constraints: 1 <= arr.length <= 300 1 <= arr[0].length <= 300 0 <= arr[i][j] <= 1
解法：
动态规划DP
dp[i][j]：代表，以matrix[i][j]为右下角的正方形的个数。
动态转移方程：
如果该节点matrix[i][j]==1:
dp[i][j]=min(dp[i-1][j-1], dp[i-1][j], dp[i][j-1]) +1
如果该节点matrix[i][j]==0:
dp[i][j]=0=matrix[i][j]
代码参考：
1 class Solution { 2 public: 3 int countSquares(vector<vector<int>>& matrix) { 4 int m=matrix.size(), n=matrix[0].size(); 5 int res=0; 6 for(int i=0; i<m; i++){ 7 for(int j=0; j<n; j++){ 8 if(i>0 && j>0 && matrix[i][j]>0){ 9 matrix[i][j] = min(matrix[i-1][j-1], min(matrix[i-1][j], matrix[i][j-1]))+1; 10 } 11 res+=matrix[i][j]; 12 } 13 } 14 return res; 15 } 16 };
1277. Count Square Submatrices with All Ones
标签：规划 class exp 问题 span return ber ++ size
原文地址：https://www.cnblogs.com/habibah-chang/p/13209950.html
