day33打卡

8. K次取反后最大化的数组和

var largestSumAfterKNegations = function(nums, k) {
    const freq = new Map();
    for (const num of nums) {
        freq.set(num, (freq.get(num) || 0) + 1);
    }
    let ans = _.sum(nums);
    for (let i = -100; i < 0; ++i) {
        if (freq.has(i)) {
            const ops = Math.min(k, freq.get(i));
            ans += (-i) * ops * 2;
            freq.set(i, freq.get(i) - ops);
            freq.set(-i, (freq.get(-i) || 0) + ops);
            k -= ops;
            if (k === 0) {
                break;
            }
        }
    }
    if (k > 0 && k % 2 === 1 && !freq.has(0)) {
        for (let i = 1; i <= 100; ++i) {
            if (freq.has(i)) {
                ans -= i * 2;
                break;
            }
        }
    }
    return ans;
};

9. 加油站

var canCompleteCircuit = function(gas, cost) {
    const n = gas.length;
    let i = 0;
    while (i < n) {
        let sumOfGas = 0, sumOfCost = 0;
        let cnt = 0;
        while (cnt < n) {
            const j = (i + cnt) % n;
            sumOfGas += gas[j];
            sumOfCost += cost[j];
            if (sumOfCost > sumOfGas) {
                break;
            }
            cnt++;
        }
        if (cnt === n) {
            return i;
        } else {
            i = i + cnt + 1;
        }
    }
    return -1;
};

10. 分发糖果

var candy = function(ratings) {
    const n = ratings.length;
    const left = new Array(n).fill(0);
    for (let i = 0; i < n; i++) {
        if (i > 0 && ratings[i] > ratings[i - 1]) {
            left[i] = left[i - 1] + 1;
        } else {
            left[i] = 1;
        }
    }

    let right = 0, ret = 0;
    for (let i = n - 1; i > -1; i--) {
        if (i < n - 1 && ratings[i] > ratings[i + 1]) {
            right++;
        } else {
            right = 1;
        }
        ret += Math.max(left[i], right);
    }
    return ret;
};