diff options
Diffstat (limited to 'min_falling_path_sum.cpp')
-rw-r--r-- | min_falling_path_sum.cpp | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/min_falling_path_sum.cpp b/min_falling_path_sum.cpp new file mode 100644 index 0000000..33c1cd8 --- /dev/null +++ b/min_falling_path_sum.cpp @@ -0,0 +1,45 @@ +#include "leetcode.h" + +/* + * given NxN array of integers 'matrix' return the minimum + * sum of any falling path through 'matrix' + * + * a falling path starts at any element in row 0 and chooses + * the element in the next row that is either directly below + * or diagonally left/right that obviously makes for the lowest sum + */ + +class Solution { +public: + int minFallingPathSum(vvd(int) & matrix) { + vvd(int) dp(matrix.size(), vector<int>(matrix.size(), INT_MAX)); + for (int i = 0; i < matrix.size(); i++) + dp[0][i] = matrix[0][i]; + for (int i = 1; i < matrix.size(); i++) { + for (int j = 0; j < matrix.size(); j++) { + if (j > 0 && j < matrix.size() - 1) { + dp[i][j] = + min(dp[i - 1][j - 1] + matrix[i][j], dp[i - 1][j] + matrix[i][j]); + dp[i][j] = min(dp[i - 1][i + 1] + matrix[i][j], dp[i][j]); + } else if (j == 0) + dp[i][j] = + min(dp[i - 1][j + 1] + matrix[i][j], dp[i - 1][j] + matrix[i][j]); + else if (j == matrix.size() - 1) + dp[i][j] = + min(dp[i - 1][j - 1] + matrix[i][j], dp[i - 1][j] + matrix[i][j]); + } + } + int ans = INT_MAX; + for (auto &x : dp[dp.size() - 1]) + ans = min(ans, x); + return ans; + } +}; + +int main() { + Solution obj; + vvd(int) matrix = {{2, 1, 3}, // 1 + {6, 5, 4}, //-> 4 + {7, 8, 9}}; // 8 <- + cout << obj.minFallingPathSum(matrix); // expect 13 +} |