1074. 元素和为目标值的子矩阵数量

/**
 * @param {number[][]} matrix
 * @param {number} target
 * @return {number}
 */
var numSubmatrixSumTarget = function(matrix, target) {
    let m = matrix.length;
    let n = matrix[0].length;
    let res = 0;
    for(let i = 0;i<m;i++){
        let sum = new Array(n).fill(0);
        for(let j=i;j<m;j++){
            for(let k=0;k<n;k++){
                sum[k] +=matrix[j][k];
            }
            res+=findSumTarget(sum,target);
        }
    }
    function  findSumTarget (sum,k) {
        let map = new Map();
        map.set(0,1);
        let pre = 0;
        let count = 0;
        for(num of sum){
            pre+=num;
            if(map.has(pre-k)){
                count+= map.get(pre-k)
            }
            map.set(pre, (map.get(pre)||0) + 1)
        }
        return count;
    }
    return res;
};

let matrix = [[0,1,0],[1,1,1],[0,1,0]], target = 0
console.log(matrix, target, numSubmatrixSumTarget(matrix,target))
matrix = [[1,-1],[-1,1]], target = 0
console.log(matrix, target, numSubmatrixSumTarget(matrix,target))
matrix = [[904]], target = 0
console.log(matrix, target, numSubmatrixSumTarget(matrix,target))