Minimum Falling Path Sum
给一个矩阵, 每个格子都能往下面的相邻的格子落, 问怎么落的相加后的和最小.
这题就是典型的矩阵dp.
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class Solution { public int minFallingPathSum(int[][] matrix) { int n = matrix.length; int[][] dp = new int[n][n]; // dp[i][j] = the min falling path sum to the current cell [i][j] for(int i = 0; i < n; i++){ dp[0][i] = matrix[0][i]; } for(int i = 1; i < n; i++) { for(int j = 0; j < n; j++) { dp[i][j] = Math.min(Math.min(j > 0 ? dp[i - 1][j - 1] : Integer.MAX_VALUE, dp[i - 1][j]), j < n - 1 ? dp[i - 1][j + 1] : Integer.MAX_VALUE) + matrix[i][j]; } } int res = Integer.MAX_VALUE; for(int i = 0; i < n; i++){ res = Math.min(dp[n - 1][i],res); } return res; } } |