Leetcode 931 Minimum Falling Path Sum

Author: jiajionline

0931_Minimum Falling Path Sum/MinimumFallingPathSum_NoCopy.java

@@ -1,27 +1,19 @@
 class Solution {
  public int minFallingPathSum(int[][] matrix) {
- int m = matrix.length;
- int n = matrix[0].length;
- 
- for(int i=m-2;i>=0;i--)
- {
- for(int j=0;j<n;j++)
- {
- if(j == 0) {
- matrix[i][j] += Math.min(matrix[i+1][j], matrix[i+1][j+1]);
- }else if(j == n-1) {
- matrix[i][j] += Math.min(matrix[i+1][j-1], matrix[i+1][j]);
- }else{
- matrix[i][j] += Math.min(matrix[i+1][j-1], Math.min(matrix[i+1][j], matrix[i+1][j+1]));
- }
+ int m = matrix.length, n = matrix[0].length;
+ for(int row=1;row<m;row++) {
+ for(int col=0;col<n;col++) {
+ int leftTop = col == 0 ? Integer.MAX_VALUE : matrix[row-1][col-1];
+ int top = matrix[row-1][col];
+ int rightTop = col == n-1 ? Integer.MAX_VALUE : matrix[row-1][col+1];
+ matrix[row][col] += ( Math.min(leftTop, Math.min(top, rightTop)));
  }
  }
- 
- int ans = matrix[0][0];
- 
- for(int i=1;i<n;i++)
- ans = Math.min(ans, matrix[0][i]);
- 
+
+ int ans = Integer.MAX_VALUE;
+ for(int i=0;i<n;i++) {
+ ans = Math.min(ans, matrix[m-1][i]);
+ }
  return ans;
  }
 }